path: root/CHANGES

-*- coding: utf-8; fill-column: 68 -*-

=======
CHANGES
=======

0.8.0b1
=======
Changes noted below are specific to version 0.8.
For changes that are in both 0.7 and 0.8, see below
underneath "0.7.xx".

- general
  - SQLAlchemy 0.8 now targets Python 2.5 and
    above.  Python 2.4 is no longer supported.

  - [removed] The "sqlalchemy.exceptions"
    synonym for "sqlalchemy.exc" is removed
    fully.  [ticket:2433]

- orm
  - [removed] The legacy "mutable" system of the
    ORM, including the MutableType class as well
    as the mutable=True flag on PickleType
    and postgresql.ARRAY has been removed.
    In-place mutations are detected by the ORM
    using the sqlalchemy.ext.mutable extension,
    introduced in 0.7.   The removal of MutableType
    and associated constructs removes a great
    deal of complexity from SQLAlchemy's internals.
    The approach performed poorly as it would incur
    a scan of the full contents of the Session
    when in use. [ticket:2442]

  - [moved] The InstrumentationManager interface
    and the entire related system of alternate
    class implementation is now moved out
    to sqlalchemy.ext.instrumentation.   This is
    a seldom used system that adds significant
    complexity and overhead to the mechanics of
    class instrumentation.  The new architecture
    allows it to remain unused until
    InstrumentationManager is actually imported,
    at which point it is bootstrapped into
    the core.

  - [feature] Major rewrite of relationship()
    internals now allow join conditions which
    include columns pointing to themselves
    within composite foreign keys.   A new
    API for very specialized primaryjoin conditions
    is added, allowing conditions based on
    SQL functions, CAST, etc. to be handled
    by placing the annotation functions
    remote() and foreign() inline within the
    expression when necessary.  Previous recipes
    using the semi-private _local_remote_pairs
    approach can be upgraded to this new
    approach. [ticket:1401]

  - [bug] ORM will perform extra effort to determine
    that an FK dependency between two tables is
    not significant during flush if the tables
    are related via joined inheritance and the FK
    dependency is not part of the inherit_condition,
    saves the user a use_alter directive.
    [ticket:2527]

  - [feature] New standalone function with_polymorphic()
    provides the functionality of query.with_polymorphic()
    in a standalone form.   It can be applied to any
    entity within a query, including as the target
    of a join in place of the "of_type()" modifier.
    [ticket:2333]

  - [feature] The of_type() construct on attributes
    now accepts aliased() class constructs as well
    as with_polymorphic constructs, and works with
    query.join(), any(), has(), and also
    eager loaders subqueryload(), joinedload(),
    contains_eager()
    [ticket:2438] [ticket:1106]

  - [bug] with_polymorphic() produces JOINs
    in the correct order and with correct inheriting
    tables in the case of sending multi-level
    subclasses in an arbitrary order or with
    intermediary classes missing.  [ticket:1900]

  - [feature] The "deferred declarative
    reflection" system has been moved into the
    declarative extension itself, using the
    new DeferredReflection class.  This
    class is now tested with both single
    and joined table inheritance use cases.
    [ticket:2485]

  - [feature] Added new core function "inspect()",
    which serves as a generic gateway to
    introspection into mappers, objects,
    others.   The Mapper and InstanceState
    objects have been enhanced with a public
    API that allows inspection of mapped
    attributes, including filters for column-bound
    or relationship-bound properties, inspection
    of current object state, history of
    attributes, etc.  [ticket:2208]

  - [feature] Calling rollback() within a
    session.begin_nested() will now only expire
    those objects that had net changes within the
    scope of that transaction, that is objects which
    were dirty or were modified on a flush.  This
    allows the typical use case for begin_nested(),
    that of altering a small subset of objects, to
    leave in place the data from the larger enclosing
    set of objects that weren't modified in
    that sub-transaction.  [ticket:2452]

  - [feature] Added utility feature
    Session.enable_relationship_loading(),
    supersedes relationship.load_on_pending.
    Both features should be avoided, however.
    [ticket:2372]

  - [feature] Added support for .info dictionary argument to
    column_property(), relationship(), composite().
    All MapperProperty classes have an auto-creating .info
    dict available overall.

  - [feature] Adding/removing None from a mapped collection
    now generates attribute events.  Previously, a None
    append would be ignored in some cases.  Related
    to [ticket:2229].

  - [feature] The presence of None in a mapped collection
    now raises an error during flush.   Previously,
    None values in collections would be silently ignored.
    [ticket:2229]

  - [feature] The Query.update() method is now
    more lenient as to the table
    being updated.  Plain Table objects are better
    supported now, and additional a joined-inheritance
    subclass may be used with update(); the subclass
    table will be the target of the update,
    and if the parent table is referenced in the
    WHERE clause, the compiler will call upon
    UPDATE..FROM syntax as allowed by the dialect
    to satisfy the WHERE clause.  MySQL's multi-table
    update feature is also supported if columns
    are specified by object in the "values" dicitionary.
    PG's DELETE..USING is also not available
    in Core yet.

  - [bug] Improvements to joined/subquery eager
    loading dealing with chains of subclass entities
    sharing a common base, with no specific "join depth"
    provided.  Will chain out to
    each subclass mapper individually before detecting
    a "cycle", rather than considering the base class
    to be the source of the "cycle".  [ticket:2481]

  - [bug] The "passive" flag on Session.is_modified()
    no longer has any effect. is_modified() in
    all cases looks only at local in-memory
    modified flags and will not emit any
    SQL or invoke loader callables/initializers.
    [ticket:2320]

  - [bug] The warning emitted when using
    delete-orphan cascade with one-to-many
    or many-to-many without single-parent=True
    is now an error.  The ORM
    would fail to function subsequent to this
    warning in any case.  [ticket:2405]

  - [bug] Lazy loads emitted within flush events
    such as before_flush(), before_update(),
    etc. will now function as they would
    within non-event code, regarding consideration
    of the PK/FK values used in the lazy-emitted
    query.   Previously,
    special flags would be established that
    would cause lazy loads to load related items
    based on the "previous" value of the
    parent PK/FK values specifically when called
    upon within a flush; the signal to load
    in this way is now localized to where the
    unit of work actually needs to load that
    way.  Note that the UOW does
    sometimes load these collections before
    the before_update() event is called,
    so the usage of "passive_updates" or not
    can affect whether or not a collection will
    represent the "old" or "new" data, when
    accessed within a flush event, based
    on when the lazy load was emitted.
    The change is backwards incompatible in
    the exceedingly small chance that
    user event code depended on the old
    behavior. [ticket:2350]

  - [feature] Query now "auto correlates" by
    default in the same way as select() does.
    Previously, a Query used as a subquery
    in another would require the correlate()
    method be called explicitly in order to
    correlate a table on the inside to the
    outside.  As always, correlate(None)
    disables correlation.  [ticket:2179]

  - [feature] The after_attach event is now
    emitted after the object is established
    in Session.new or Session.identity_map
    upon Session.add(), Session.merge(),
    etc., so that the object is represented
    in these collections when the event
    is called.  Added before_attach
    event to accommodate use cases that
    need autoflush w pre-attached object.
    [ticket:2464]

  - [feature] ORM entities can be passed
    to select() as well as the select_from(),
    correlate(), and correlate_except()
    methods, where they will be unwrapped
    into selectables. [ticket:2245]

  - [feature] The registry of classes
    in declarative_base() is now a
    WeakValueDictionary.  So subclasses of
    "Base" that are dereferenced will be
    garbage collected, *if they are not
    referred to by any other mappers/superclass
    mappers*. See the next note for this ticket.
    [ticket:2526]

  - [feature] Conflicts between columns on
    single-inheritance declarative subclasses,
    with or without using a mixin, can be resolved
    using a new @declared_attr usage described
    in the documentation.  [ticket:2472]

  - [feature] declared_attr can now be used
    on non-mixin classes, even though this is generally
    only useful for single-inheritance subclass
    column conflict resolution.  [ticket:2472]

  - [feature] declared_attr can now be used with
    attributes that are not Column or MapperProperty;
    including any user-defined value as well
    as association proxy objects.  [ticket:2517]

  - [bug] Fixed a disconnect that slowly evolved
    between a @declared_attr Column and a
    directly-defined Column on a mixin. In both
    cases, the Column will be applied to the
    declared class' table, but not to that of a
    joined inheritance subclass.   Previously,
    the directly-defined Column would be placed
    on both the base and the sub table, which isn't
    typically what's desired.  [ticket:2565]

  - [feature] *Very limited* support for
    inheriting mappers to be GC'ed when the
    class itself is deferenced.  The mapper
    must not have its own table (i.e.
    single table inh only) without polymorphic
    attributes in place.
    This allows for the use case of
    creating a temporary subclass of a declarative
    mapped class, with no table or mapping
    directives of its own, to be garbage collected
    when dereferenced by a unit test.
    [ticket:2526]

  - [feature] Declarative now maintains a registry
    of classes by string name as well as by full
    module-qualified name.   Multiple classes with the
    same name can now be looked up based on a module-qualified
    string within relationship().   Simple class name
    lookups where more than one class shares the same
    name now raises an informative error message.
    [ticket:2338]

  - [feature] Can now provide class-bound attributes
    that override columns which are of any
    non-ORM type, not just descriptors.
    [ticket:2535]

  - [feature] Added with_labels and
    reduce_columns keyword arguments to
    Query.subquery(), to provide two alternate
    strategies for producing queries with uniquely-
    named columns.  [ticket:1729].

  - [feature] A warning is emitted when a reference
    to an instrumented collection is no longer
    associated with the parent class due to
    expiration/attribute refresh/collection
    replacement, but an append
    or remove operation is received on the
    now-detached collection.  [ticket:2476]

  - [bug] Declarative can now propagate a column
    declared on a single-table inheritance subclass
    up to the parent class' table, when the parent
    class is itself mapped to a join() or select()
    statement, directly or via joined inheritance,
    and not just a Table.   [ticket:2549]

  - [bug] An error is emitted when uselist=False
    is combined with a "dynamic" loader.
    This is a warning in 0.7.9.

  - [removed] Deprecated identifiers removed:

    * allow_null_pks mapper() argument
      (use allow_partial_pks)

    * _get_col_to_prop() mapper method
      (use get_property_by_column())

    * dont_load argument to Session.merge()
      (use load=True)

    * sqlalchemy.orm.shard module
      (use sqlalchemy.ext.horizontal_shard)

- engine
  - [feature] Connection event listeners can
    now be associated with individual
    Connection objects, not just Engine
    objects.  [ticket:2511]

  - [feature] The before_cursor_execute event
    fires off for so-called "_cursor_execute"
    events, which are usually special-case
    executions of primary-key bound sequences
    and default-generation SQL
    phrases that invoke separately when RETURNING
    is not used with INSERT.  [ticket:2459]

  - [bug] Fixed bug whereby if a database restart
    affected multiple connections, each
    connection would individually invoke a new
    disposal of the pool, even though only
    one disposal is needed.  [ticket:2522]

  - [feature] Added a new system
    for registration of new dialects in-process
    without using an entrypoint.  See the
    docs for "Registering New Dialects".
    [ticket:2462]

  - [feature] The "required" flag is set to
    True by default, if not passed explicitly,
    on bindparam() if the "value" or "callable"
    parameters are not passed.
    This will cause statement execution to check
    for the parameter being present in the final
    collection of bound parameters, rather than
    implicitly assigning None. [ticket:2556]

  - [bug] The names of the columns on the
    .c. attribute of a select().apply_labels()
    is now based on <tablename>_<colkey> instead
    of <tablename>_<colname>, for those columns
    that have a distinctly named .key.
    [ticket:2397]

  - [feature] Inspector.get_primary_keys() is
    deprecated; use Inspector.get_pk_constraint().
    Courtesy Diana Clarke.  [ticket:2422]

  - [bug] The autoload_replace flag on Table,
    when False, will cause any reflected foreign key
    constraints which refer to already-declared
    columns to be skipped, assuming that the
    in-Python declared column will take over
    the task of specifying in-Python ForeignKey
    or ForeignKeyConstraint declarations.

  - [bug] The ResultProxy methods inserted_primary_key,
    last_updated_params(), last_inserted_params(),
    postfetch_cols(), prefetch_cols() all
    assert that the given statement is a compiled
    construct, and is an insert() or update()
    statement as is appropriate, else
    raise InvalidRequestError.  [ticket:2498]

  - [feature] New C extension module "utils" has
    been added for additional function speedups
    as we have time to implement.

  - ResultProxy.last_inserted_ids is removed,
    replaced by inserted_primary_key.

- sql
  - [feature] Major rework of operator system
    in Core, to allow redefinition of existing
    operators as well as addition of new operators
    at the type level.  New types can be created
    from existing ones which add or redefine
    operations that are exported out to column
    expressions, in a similar manner to how the
    ORM has allowed comparator_factory.   The new
    architecture moves this capability into the
    Core so that it is consistently usable in
    all cases, propagating cleanly using existing
    type propagation behavior.  [ticket:2547]

  - [feature] To complement [ticket:2547], types
    can now provide "bind expressions" and
    "column expressions" which allow compile-time
    injection of SQL expressions into statements
    on a per-column or per-bind level.   This is
    to suit the use case of a type which needs
    to augment bind- and result- behavior at the
    SQL level, as opposed to in the Python level.
    Allows for schemes like transparent encryption/
    decryption, usage of Postgis functions, etc.
    [ticket:1534]

  - [feature] The Core oeprator system now includes
    the `getitem` operator, i.e. the bracket
    operator in Python.  This is used at first
    to provide index and slice behavior to the
    Postgresql ARRAY type, and also provides a hook
    for end-user definition of custom __getitem__
    schemes which can be applied at the type
    level as well as within ORM-level custom
    operator schemes.   `lshift` (<<)
    and `rshift` (>>) are also supported as
    optional operators.

    Note that this change has the effect that
    descriptor-based __getitem__ schemes used by
    the ORM in conjunction with synonym() or other
    "descriptor-wrapped" schemes will need
    to start using a custom comparator in order
    to maintain this behavior.

  - [feature] Revised the rules used to determine
    the operator precedence for the user-defined
    operator, i.e. that granted using the ``op()``
    method.   Previously, the smallest precedence
    was applied in all cases, now the default
    precedence is zero, lower than all operators
    except "comma" (such as, used in the argument
    list of a ``func`` call) and "AS", and is
    also customizable via the "precedence" argument
    on the ``op()`` method.  [ticket:2537]

  - [feature] Custom unary operators can now be
    used by combining operators.custom_op() with
    UnaryExpression().

  - [feature] Enhanced GenericFunction and func.*
    to allow for user-defined GenericFunction
    subclasses to be available via the func.*
    namespace automatically by classname,
    optionally using a package name, as well
    as with the ability to have the rendered
    name different from the identified name
    in func.*.

  - [feature] The cast() and extract() constructs
    will now be produced via the func.* accessor
    as well, as users naturally try to access these
    names from func.* they might as well do
    what's expected, even though the returned
    object is not a FunctionElement.
    [ticket:2562]

  - [changed] Most classes in expression.sql
    are no longer preceded with an underscore,
    i.e. Label, SelectBase, Generative, CompareMixin.
    _BindParamClause is also renamed to
    BindParameter.   The old underscore names for
    these classes will remain available as synonyms
    for the foreseeable future.

  - [feature] The Inspector object can now be
    acquired using the new inspect() service,
    part of [ticket:2208]

  - [feature] The column_reflect event now
    accepts the Inspector object as the first
    argument, preceding "table".   Code which
    uses the 0.7 version of this very new
    event will need modification to add the
    "inspector" object as the first argument.
    [ticket:2418]

  - [feature] The behavior of column targeting
    in result sets is now case sensitive by
    default.   SQLAlchemy for many years would
    run a case-insensitive conversion on these values,
    probably to alleviate early case sensitivity
    issues with dialects like Oracle and
    Firebird.   These issues have been more cleanly
    solved in more modern versions so the performance
    hit of calling lower() on identifiers is removed.
    The case insensitive comparisons can be re-enabled
    by setting "case_insensitive=False" on
    create_engine().  [ticket:2423]

  - [feature] The "unconsumed column names" warning emitted
    when keys are present in insert.values() or update.values()
    that aren't in the target table is now an exception.
    [ticket:2415]

  - [feature] Added "MATCH" clause to ForeignKey,
    ForeignKeyConstraint, courtesy Ryan Kelly.
    [ticket:2502]

  - [feature] Added support for DELETE and UPDATE from
    an alias of a table, which would assumedly
    be related to itself elsewhere in the query,
    courtesy Ryan Kelly.  [ticket:2507]

  - [feature] select() features a correlate_except()
    method, auto correlates all selectables except those
    passed.

  - [feature] The prefix_with() method is now available
    on each of select(), insert(), update(), delete(),
    all with the same API, accepting multiple
    prefix calls, as well as a "dialect name" so that
    the prefix can be limited to one kind of dialect.
    [ticket:2431]

  - [feature] Added reduce_columns() method
    to select() construct, replaces columns inline
    using the util.reduce_columns utility function
    to remove equivalent columns.  reduce_columns()
    also adds "with_only_synonyms" to limit the
    reduction just to those columns which have the same
    name.  The deprecated fold_equivalents() feature is
    removed [ticket:1729].

  - [feature] Reworked the startswith(), endswith(),
    contains() operators to do a better job with
    negation (NOT LIKE), and also to assemble them
    at compilation time so that their rendered SQL
    can be altered, such as in the case for Firebird
    STARTING WITH [ticket:2470]

  - [feature] Added a hook to the system of rendering
    CREATE TABLE that provides access to the render for each
    Column individually, by constructing a @compiles
    function against the new schema.CreateColumn
    construct.  [ticket:2463]

  - [bug] Fixes to the interpretation of the
    Column "default" parameter as a callable
    to not pass ExecutionContext into a keyword
    argument parameter.  [ticket:2520]

  - [bug] All of UniqueConstraint, ForeignKeyConstraint,
    CheckConstraint, and PrimaryKeyConstraint will
    attach themselves to their parent table automatically
    when they refer to a Table-bound Column object directly
    (i.e. not just string column name), and refer to
    one and only one Table.   Prior to 0.8 this behavior
    occurred for UniqueConstraint and PrimaryKeyConstraint,
    but not ForeignKeyConstraint or CheckConstraint.
    [ticket:2410]

  - [bug] column.label(None) now produces an
    anonymous label, instead of returning the
    column object itself, consistent with the behavior
    of label(column, None).  [ticket:2168]

- sqlite
  - [feature] the SQLite date and time types
    have been overhauled to support a more open
    ended format for input and output, using
    name based format strings and regexps.  A
    new argument "microseconds" also provides
    the option to omit the "microseconds"
    portion of timestamps.  Thanks to
    Nathan Wright for the work and tests on
    this.  [ticket:2363]

- mssql
  - [feature] SQL Server dialect can be given
    database-qualified schema names,
    i.e. "schema='mydatabase.dbo'"; reflection
    operations will detect this, split the schema
    among the "." to get the owner separately,
    and emit a "USE mydatabase" statement before
    reflecting targets within the "dbo" owner;
    the existing database returned from
    DB_NAME() is then restored.

  - [bug] removed legacy behavior whereby
    a column comparison to a scalar SELECT via
    == would coerce to an IN with the SQL server
    dialect.  This is implicit
    behavior which fails in other scenarios
    so is removed.  Code which relies on this
    needs to be modified to use column.in_(select)
    explicitly.  [ticket:2277]

- postgresql

  - [feature] postgresql.ARRAY features an optional
    "dimension" argument, will assign a specific
    number of dimensions to the array which will
    render in DDL as ARRAY[][]..., also improves
    performance of bind/result processing.
    [ticket:2441]

  - [feature] postgresql.ARRAY now supports
    indexing and slicing.  The Python [] operator
    is available on all SQL expressions that are
    of type ARRAY; integer or simple slices can be
    passed.  The slices can also be used on the
    assignment side in the SET clause of an UPDATE
    statement by passing them into Update.values();
    see the docs for examples.

  - [feature] Added new "array literal" construct
    postgresql.array().  Basically a "tuple" that
    renders as ARRAY[1,2,3].

  - [feature] Added support for the Postgresql ONLY
    keyword, which can appear corresponding to a
    table in a SELECT, UPDATE, or DELETE statement.
    The phrase is established using with_hint().
    Courtesy Ryan Kelly [ticket:2506]

  - [feature] The "ischema_names" dictionary of the
    Postgresql dialect is "unofficially" customizable.
    Meaning, new types such as PostGIS types can
    be added into this dictionary, and the PG type
    reflection code should be able to handle simple
    types with variable numbers of arguments.
    The functionality here is "unofficial" for
    three reasons:

    1. this is not an "official" API.  Ideally
       an "official" API would allow custom type-handling
       callables at the dialect or global level
       in a generic way.
    2. This is only implemented for the PG dialect,
       in particular because PG has broad support
       for custom types vs. other database backends.
       A real API would be implemented at the
       default dialect level.
    3. The reflection code here is only tested against
       simple types and probably has issues with more
       compositional types.

    patch courtesy Éric Lemoine.

- firebird
  - [feature] The "startswith()" operator renders
    as "STARTING WITH", "~startswith()" renders
    as "NOT STARTING WITH", using FB's more efficient
    operator.  [ticket:2470]

  - [bug] CompileError is raised when VARCHAR with
    no length is attempted to be emitted, same
    way as MySQL. [ticket:2505]

- mysql
  - [bug] Dialect no longer emits expensive server
    collations query, as well as server casing,
    on first connect.  These functions are still
    available as semi-private. [ticket:2404]

- oracle
  - [bug] Quoting information is now passed along
    from a Column with quote=True when generating
    a same-named bound parameter to the bindparam()
    object, as is the case in generated INSERT and UPDATE
    statements, so that unknown reserved names can
    be fully supported.  [ticket:2437]

  - [feature] The types of columns excluded from the
    setinputsizes() set can be customized by sending
    a list of string DBAPI type names to exclude.
    This list was previously fixed.  The list also
    now defaults to STRING, UNICODE, removing
    CLOB, NCLOB from the list.  [ticket:2469]

- extensions
  - [removed] The SQLSoup extension is removed from
    SQLAlchemy, and is now an external project.
    See http://pypi.python.org/pypi/sqlsoup .
    [ticket:2262]

0.7.7 - 0.7.xx
==============
0.8 development begins during 0.7.7 development.
All relevant bug fixes
and features listed below from version 0.7.7 on
are also present in 0.8.

0.7.9
=====
- orm
  - [bug] Fixed bug mostly local to new
    AbstractConcreteBase helper where the "type"
    attribute from the superclass would not
    be overridden on the subclass to produce the
    "reserved for base" error message, instead placing
    a do-nothing attribute there.  This was inconsistent
    vs. using ConcreteBase as well as all the behavior
    of classical concrete mappings, where the "type"
    column from the polymorphic base would be explicitly
    disabled on subclasses, unless overridden
    explicitly.

  - [bug] A warning is emitted when lazy='dynamic'
    is combined with uselist=False.  This is an
    exception raise in 0.8.

  - [bug] Fixed bug whereby user error in related-object
    assignment could cause recursion overflow if the
    assignment triggered a backref of the same name
    as a bi-directional attribute on the incorrect
    class to the same target.  An informative
    error is raised now.

  - [bug] Fixed bug where incorrect type information
    would be passed when the ORM would bind the
    "version" column, when using the "version" feature.
    Tests courtesy Daniel Miller.  [ticket:2539]

- sql
  - [bug] Fixed CTE bug whereby positional
    bound parameters present in the CTEs themselves
    would corrupt the overall ordering of
    bound parameters.  This primarily
    affected SQL Server as the platform with
    positional binds + CTE support.
    [ticket:2521]

  - [bug] Fixed more un-intuitivenesses in CTEs
    which prevented referring to a CTE in a union
    of itself without it being aliased.
    CTEs now render uniquely
    on name, rendering the outermost CTE of a given
    name only - all other references are rendered
    just as the name.   This even includes other
    CTE/SELECTs that refer to different versions
    of the same CTE object, such as a SELECT
    or a UNION ALL of that SELECT. We are
    somewhat loosening the usual link between object
    identity and lexical identity in this case.
    A true name conflict between two unrelated
    CTEs now raises an error.

  - [bug] quoting is applied to the column names
    inside the WITH RECURSIVE clause of a
    common table expression according to the
    quoting rules for the originating Column.
    [ticket:2512]

  - [bug] Fixed regression introduced in 0.7.6
    whereby the FROM list of a SELECT statement
    could be incorrect in certain "clone+replace"
    scenarios.  [ticket:2518]

  - [bug] Fixed bug whereby usage of a UNION
    or similar inside of an embedded subquery
    would interfere with result-column targeting,
    in the case that a result-column had the same
    ultimate name as a name inside the embedded
    UNION. [ticket:2552]

  - [bug] Fixed a regression since 0.6 regarding
    result-row targeting.   It should be possible
    to use a select() statement with string
    based columns in it, that is
    select(['id', 'name']).select_from('mytable'),
    and have this statement be targetable by
    Column objects with those names; this is the
    mechanism by which
    query(MyClass).from_statement(some_statement)
    works.  At some point the specific case of
    using select(['id']), which is equivalent to
    select([literal_column('id')]), stopped working
    here, so this has been re-instated and of
    course tested. [ticket:2558]

- engine
  - [bug] Fixed bug whereby
    a disconnect detect + dispose that occurs
    when the QueuePool has threads waiting
    for connections would leave those
    threads waiting for the duration of
    the timeout on the old pool (or indefinitely
    if timeout was disabled).   The fix
    now notifies those waiters with a special
    exception case and has them move onto
    the new pool.  [ticket:2522]

  - [feature] Dramatic improvement in memory
    usage of the event system; instance-level
    collections are no longer created for a
    particular type of event until
    instance-level listeners are established
    for that event.  [ticket:2516]

  - [bug] Added gaerdbms import to mysql/__init__.py,
    the absense of which was preventing the new
    GAE dialect from being loaded.  [ticket:2529]

  - [bug] Fixed cextension bug whereby the
    "ambiguous column error" would fail to
    function properly if the given index were
    a Column object and not a string.
    Note there are still some column-targeting
    issues here which are fixed in 0.8.
    [ticket:2553]

  - [bug] Fixed the repr() of Enum to include
    the "name" and "native_enum" flags.  Helps
    Alembic autogenerate.

- sqlite
  - [bug] Adjusted a very old bugfix which attempted
    to work around a SQLite issue that itself was
    "fixed" as of sqlite 3.6.14, regarding quotes
    surrounding a table name when using
    the "foreign_key_list" pragma.  The fix has been
    adjusted to not interfere with quotes that
    are *actually in the name* of a column or table,
    to as much a degree as possible; sqlite still
    doesn't return the correct result for foreign_key_list()
    if the target table actually has quotes surrounding
    its name, as *part* of its name (i.e. """mytable""").
    [ticket:2568]

- mysql
  - [bug] Updated mysqlconnector interface to use
    updated "client flag" and "charset" APIs,
    courtesy David McNelis.

- mssql
  - [bug] Fixed compiler bug whereby a given
    select() would be modified if it had an "offset"
    attribute, causing the construct to not compile
    correctly a second time.  [ticket:2545]

0.7.8
=====
- orm
  - [bug] Fixed bug whereby subqueryload() from
    a polymorphic mapping to a target would incur
    a new invocation of the query for each
    distinct class encountered in the polymorphic
    result.  [ticket:2480]

  - [bug] Fixed bug in declarative
    whereby the precedence of columns
    in a joined-table, composite
    column (typically for id) would fail to
    be correct if the columns contained
    names distinct from their attribute
    names.  This would cause things like
    primaryjoin conditions made against the
    entity attributes to be incorrect.  Related
    to [ticket:1892] as this was supposed
    to be part of that, this is [ticket:2491].

  - [feature] The 'objects' argument to
    flush() is no longer deprecated, as some
    valid use cases have been identified.

  - [bug] Fixed identity_key() function which
    was not accepting a scalar argument
    for the identity.  [ticket:2508].

  - [bug] Fixed bug whereby populate_existing
    option would not propagate to subquery
    eager loaders.  [ticket:2497].

- sql
  - [bug] added BIGINT to types.__all__,
    BIGINT, BINARY, VARBINARY to sqlalchemy
    module namespace, plus test to ensure
    this breakage doesn't occur again.
    [ticket:2499]

  - [bug] Repaired common table expression
    rendering to function correctly when the
    SELECT statement contains UNION or other
    compound expressions, courtesy btbuilder.
    [ticket:2490]

  - [bug] Fixed bug whereby append_column()
    wouldn't function correctly on a cloned
    select() construct, courtesy
    Gunnlaugur Þór Briem.  [ticket:2482]

- engine
  - [bug] Fixed memory leak in C version of
    result proxy whereby DBAPIs which don't deliver
    pure Python tuples for result rows would
    fail to decrement refcounts correctly.
    The most prominently affected DBAPI
    is pyodbc.  [ticket:2489]

  - [bug] Fixed bug affecting Py3K whereby
    string positional parameters passed to
    engine/connection execute() would fail to be
    interpreted correctly, due to __iter__
    being present on Py3K string.
    [ticket:2503].

- postgresql
  - [bug] removed unnecessary table clause when
    reflecting enums, [ticket:2510].  Courtesy
    Gunnlaugur Þór Briem.

- oracle
  - [bug] Added ROWID to oracle.*, [ticket:2483]

- mysql
  - [feature] Added a new dialect for Google App
    Engine.  Courtesy Richie Foreman. [ticket:2484]


0.7.7
=====
- orm
  - [bug] Fixed issue in unit of work
    whereby setting a non-None self-referential
    many-to-one relationship to None
    would fail to persist the change if the
    former value was not already loaded.
    [ticket:2477].

  - [feature] Added prefix_with() method
    to Query, calls upon select().prefix_with()
    to allow placement of MySQL SELECT
    directives in statements.  Courtesy
    Diana Clarke [ticket:2443]

  - [bug] Fixed bug in 0.7.6 introduced by
    [ticket:2409] whereby column_mapped_collection
    used against columns that were mapped as
    joins or other indirect selectables
    would fail to function.

  - [feature] Added new flag to @validates
    include_removes.  When True, collection
    remove and attribute del events
    will also be sent to the validation function,
    which accepts an additional argument
    "is_remove" when this flag is used.

  - [bug] Fixed bug whereby polymorphic_on
    column that's not otherwise mapped on the
    class would be incorrectly included
    in a merge() operation, raising an error.
    [ticket:2449]

  - [bug] Fixed bug in expression annotation
    mechanics which could lead to incorrect
    rendering of SELECT statements with aliases
    and joins, particularly when using
    column_property().  [ticket:2453]

  - [bug] Fixed bug which would prevent
    OrderingList from being pickleable
    [ticket:2454].  Courtesy Jeff Dairiki

  - [bug] Fixed bug in relationship comparisons
    whereby calling unimplemented methods like
    SomeClass.somerelationship.like() would
    produce a recursion overflow, instead
    of NotImplementedError.

- sql
  - [bug] Removed warning when Index is created
    with no columns; while this might not be what
    the user intended, it is a valid use case
    as an Index could be a placeholder for just an
    index of a certain name.

  - [feature] Added new connection event
    dbapi_error(). Is called for all DBAPI-level
    errors passing the original DBAPI exception
    before SQLAlchemy modifies the state
    of the cursor.

  - [bug] If conn.begin() fails when calling
    "with engine.begin()", the newly acquired
    Connection is closed explicitly before
    propagating the exception onward normally.

  - [bug] Add BINARY, VARBINARY to types.__all__,
    [ticket:2474]

- mssql
  - [feature] Added interim create_engine flag
    supports_unicode_binds to PyODBC dialect,
    to force whether or not the dialect
    passes Python unicode literals to PyODBC
    or not.

  - [bug] Repaired the use_scope_identity
    create_engine() flag when using the pyodbc
    dialect.  Previously this flag would be
    ignored if set to False.  When set to False,
    you'll get "SELECT @@identity" after each
    INSERT to get at the last inserted ID,
    for those tables which have "implicit_returning"
    set to False.

  - [bug] UPDATE..FROM syntax with SQL Server
    requires that the updated table be present
    in the FROM clause when an alias of that
    table is also present in the FROM clause.
    The updated table is now always present
    in the FROM, when FROM is present
    in the first place.  Courtesy sayap.
    [ticket:2468]

- postgresql
  - [feature] Added new for_update/with_lockmode()
    options for Postgresql: for_update="read"/
    with_lockmode("read"),
    for_update="read_nowait"/
    with_lockmode("read_nowait").
    These emit "FOR SHARE" and "FOR SHARE NOWAIT",
    respectively.  Courtesy Diana Clarke
    [ticket:2445]

  - [bug] removed unnecessary table clause
    when reflecting domains, [ticket:2473]

- mysql
  - [bug] Fixed bug whereby column name inside
    of "KEY" clause for autoincrement composite
    column with InnoDB would double quote a
    name that's a reserved word.  Courtesy Jeff
    Dairiki. [ticket:2460]

  - [bug] Fixed bug whereby get_view_names() for
    "information_schema" schema would fail
    to retrieve views marked as "SYSTEM VIEW".
    courtesy Matthew Turland.

  - [bug] Fixed bug whereby if cast() is used
    on a SQL expression whose type is not supported
    by cast() and therefore CAST isn't rendered by
    the dialect, the order of evaluation could change
    if the casted expression required that it be
    grouped; grouping is now applied to those
    expressions.  [ticket:2467]

- sqlite

  - [feature] Added SQLite execution option
    "sqlite_raw_colnames=True", will bypass
    attempts to remove "." from column names
    returned by SQLite cursor.description.
    [ticket:2475]

0.7.6
=====
- orm
  - [bug] Fixed event registration bug
    which would primarily show up as
    events not being registered with
    sessionmaker() instances created
    after the event was associated
    with the Session class.  [ticket:2424]

  - [bug] Fixed bug whereby a primaryjoin
    condition with a "literal" in it would
    raise an error on compile with certain
    kinds of deeply nested expressions
    which also needed to render the same
    bound parameter name more than once.
    [ticket:2425]

  - [feature] Added "no_autoflush" context
    manager to Session, used with with:
    will temporarily disable autoflush.

  - [feature] Added cte() method to Query,
    invokes common table expression support
    from the Core (see below). [ticket:1859]

  - [bug] Removed the check for number of
    rows affected when doing a multi-delete
    against mapped objects.   If an ON DELETE
    CASCADE exists between two rows, we can't
    get an accurate rowcount from the DBAPI;
    this particular count is not supported
    on most DBAPIs in any case, MySQLdb
    is the notable case where it is.
    [ticket:2403]

  - [bug] Fixed bug whereby objects using
    attribute_mapped_collection or
    column_mapped_collection could not be
    pickled.  [ticket:2409]

  - [bug] Fixed bug whereby MappedCollection
    would not get the appropriate collection
    instrumentation if it were only used
    in a custom subclass that used
    @collection.internally_instrumented.
    [ticket:2406]

  - [bug] Fixed bug whereby SQL adaption mechanics
    would fail in a very nested scenario involving
    joined-inheritance, joinedload(), limit(), and a
    derived function in the columns clause.
    [ticket:2419]

  - [bug] Fixed the repr() for CascadeOptions to
    include refresh-expire.  Also reworked
    CascadeOptions to be a <frozenset>.
    [ticket:2417]

  - [feature] Added the ability to query for
    Table-bound column names when using
    query(sometable).filter_by(colname=value).
    [ticket:2400]

  - [bug] Improved the "declarative reflection"
    example to support single-table inheritance,
    multiple calls to prepare(), tables that
    are present in alternate schemas,
    establishing only a subset of classes
    as reflected.

  - [bug] Scaled back the test applied within
    flush() to check for UPDATE against partially
    NULL PK within one table to only actually
    happen if there's really an UPDATE to occur.
    [ticket:2390]

  - [bug] Fixed bug whereby if a method name
    conflicted with a column name, a
    TypeError would be raised when the mapper
    tried to inspect the __get__() method
    on the method object.  [ticket:2352]

- sql
  - [bug] Fixed memory leak in core which would
    occur when C extensions were used with
    particular types of result fetches,
    in particular when orm query.count()
    were called.  [ticket:2427]

  - [bug] Fixed issue whereby attribute-based
    column access on a row would raise
    AttributeError with non-C version,
    NoSuchColumnError with C version.  Now
    raises AttributeError in both cases.
    [ticket:2398]

  - [feature] Added support for SQL standard
    common table expressions (CTE), allowing
    SELECT objects as the CTE source (DML
    not yet supported).  This is invoked via
    the cte() method on any select() construct.
    [ticket:1859]

  - [bug] Added support for using the .key
    of a Column as a string identifier in a
    result set row.   The .key is currently
    listed as an "alternate" name for a column,
    and is superseded by the name of a column
    which has that key value as its regular name.
    For the next major release
    of SQLAlchemy we may reverse this precedence
    so that .key takes precedence, but this
    is not decided on yet.  [ticket:2392]

  - [bug] A warning is emitted when a not-present
    column is stated in the values() clause
    of an insert() or update() construct.
    Will move to an exception in 0.8.
    [ticket:2413]

  - [bug] A significant change to how labeling
    is applied to columns in SELECT statements
    allows "truncated" labels, that is label names
    that are generated in Python which exceed
    the maximum identifier length (note this is
    configurable via label_length on create_engine()),
    to be properly referenced when rendered inside
    of a subquery, as well as to be present
    in a result set row using their original
    in-Python names.   [ticket:2396]

  - [bug] Fixed bug in new "autoload_replace" flag
    which would fail to preserve the primary
    key constraint of the reflected table.
    [ticket:2402]

  - [bug] Index will raise when arguments passed
    cannot be interpreted as columns or expressions.
    Will warn when Index is created
    with no columns at all.  [ticket:2380]

- engine
  - [feature] Added "no_parameters=True" execution
    option for connections.   If no parameters
    are present, will pass the statement
    as cursor.execute(statement), thereby invoking
    the DBAPIs behavior when no parameter collection
    is present; for psycopg2 and mysql-python, this
    means not interpreting % signs in the string.
    This only occurs with this option, and not
    just if the param list is blank, as otherwise
    this would produce inconsistent behavior
    of SQL expressions that normally escape percent
    signs (and while compiling, can't know ahead of
    time if parameters will be present in
    some cases).  [ticket:2407]

  - [bug] Added execution_options() call to
    MockConnection (i.e., that used with
    strategy="mock") which acts as a pass through
    for arguments.

  - [feature] Added pool_reset_on_return argument
    to create_engine, allows control over
    "connection return" behavior.  Also added
    new arguments 'rollback', 'commit', None
    to pool.reset_on_return to allow more control
    over connection return activity. [ticket:2378]

  - [feature] Added some decent context managers
    to Engine, Connection:

        with engine.begin() as conn:
            <work with conn in a transaction>

    and:

        with engine.connect() as conn:
            <work with conn>

    Both close out the connection when done,
    commit or rollback transaction with errors
    on engine.begin().

- sqlite
  - [bug] Fixed bug in C extensions whereby
    string format would not be applied to a
    Numeric value returned as integer; this
    affected primarily SQLite which does
    not maintain numeric scale settings.
    [ticket:2432]

- mssql
  - [feature] Added support for MSSQL INSERT,
    UPDATE, and DELETE table hints, using
    new with_hint() method on UpdateBase.
    [ticket:2430]

- mysql
  - [feature] Added support for MySQL index and
    primary key constraint types
    (i.e. USING) via new mysql_using parameter
    to Index and PrimaryKeyConstraint,
    courtesy Diana Clarke.  [ticket:2386]

  - [feature] Added support for the "isolation_level"
    parameter to all MySQL dialects.  Thanks
    to mu_mind for the patch here. [ticket:2394]

- oracle
  - [feature] Added a new create_engine() flag
    coerce_to_decimal=False, disables the precision
    numeric handling which can add lots of overhead
    by converting all numeric values to
    Decimal.  [ticket:2399]

  - [bug] Added missing compilation support for
    LONG [ticket:2401]

  - [bug] Added 'LEVEL' to the list of reserved
    words for Oracle.  [ticket:2435]

- examples
  - [bug] Altered _params_from_query() function
    in Beaker example to pull bindparams from the
    fully compiled statement, as a quick means
    to get everything including subqueries in the
    columns clause, etc.

0.7.5 (January 28, 2012)
=====
- orm
  - [bug] Fixed issue where modified session state
    established after a failed flush would be committed
    as part of the subsequent transaction that
    begins automatically after manual call
    to rollback().   The state of the session is
    checked within rollback(), and if new state
    is present, a warning is emitted and
    restore_snapshot() is called a second time,
    discarding those changes. [ticket:2389]

  - [bug] Fixed regression from 0.7.4 whereby
    using an already instrumented column from a
    superclass as "polymorphic_on" failed to resolve
    the underlying Column.  [ticket:2345]

  - [bug] Raise an exception if xyzload_all() is
    used inappropriately with two non-connected
    relationships.  [ticket:2370]

  - [feature] Added "class_registry" argument to
    declarative_base().  Allows two or more declarative
    bases to share the same registry of class names.

  - [feature] query.filter() accepts multiple
    criteria which will join via AND, i.e.
    query.filter(x==y, z>q, ...)

  - [feature] Added new capability to relationship
    loader options to allow "default" loader strategies.
    Pass '*' to any of joinedload(), lazyload(),
    subqueryload(), or noload() and that becomes the
    loader strategy used for all relationships,
    except for those explicitly stated in the
    Query.  Thanks to up-and-coming contributor
    Kent Bower for an exhaustive and well
    written test suite !  [ticket:2351]

  - [bug] Fixed bug whereby event.listen(SomeClass)
    forced an entirely unnecessary compile of the
    mapper, making events very hard to set up
    at module import time (nobody noticed this ??)
    [ticket:2367]

  - [bug] Fixed bug whereby hybrid_property didn't
    work as a kw arg in any(), has().

  - Fixed regression from 0.6 whereby if
    "load_on_pending" relationship() flag were used
    where a non-"get()" lazy clause needed to be
    emitted on a pending object, it would fail
    to load.

  - [bug] ensure pickleability of all ORM exceptions
    for multiprocessing compatibility. [ticket:2371]

  - [bug] implemented standard "can't set attribute" /
    "can't delete attribute" AttributeError when
    setattr/delattr used on a hybrid that doesn't
    define fset or fdel. [ticket:2353]

  - [bug] Fixed bug where unpickled object didn't
    have enough of its state set up to work
    correctly within the unpickle() event established
    by the mutable object extension, if the object
    needed ORM attribute access within
    __eq__() or similar. [ticket:2362]

  - [bug] Fixed bug where "merge" cascade could
    mis-interpret an unloaded attribute, if the
    load_on_pending flag were used with
    relationship().  Thanks to Kent Bower
    for tests.  [ticket:2374]

  - [feature] New declarative reflection example
    added, illustrates how best to mix table reflection
    with declarative as well as uses some new features
    from [ticket:2356].

- sql
  - [feature] New reflection feature "autoload_replace";
    when set to False on Table, the Table can be autoloaded
    without existing columns being replaced.  Allows
    more flexible chains of Table construction/reflection
    to be constructed, including that it helps with
    combining Declarative with table reflection.
    See the new example on the wiki.  [ticket:2356]

  - [bug] Improved the API for add_column() such that
    if the same column is added to its own table,
    an error is not raised and the constraints
    don't get doubled up.  Also helps with some
    reflection/declarative patterns. [ticket:2356]

  - [feature] Added "false()" and "true()" expression
    constructs to sqlalchemy.sql namespace, though
    not part of __all__ as of yet.

  - [feature] Dialect-specific compilers now raise
    CompileException for all type/statement compilation
    issues, instead of InvalidRequestError or ArgumentError.
    The DDL for CREATE TABLE will re-raise
    CompileExceptions to include table/column information
    for the problematic column.  [ticket:2361]

  - [bug] Fixed issue where the "required" exception
    would not be raised for bindparam() with required=True,
    if the statement were given no parameters at all.
    [ticket:2381]

- engine
  - [bug] Added __reduce__ to StatementError,
    DBAPIError, column errors so that exceptions
    are pickleable, as when using multiprocessing.
    However, not
    all DBAPIs support this yet, such as
    psycopg2. [ticket:2371]

  - [bug] Improved error messages when a non-string
    or invalid string is passed to any of the
    date/time processors used by SQLite, including
    C and Python versions.  [ticket:2382]

  - [bug] Fixed bug whereby a table-bound Column
    object named "<a>_<b>" which matched a column
    labeled as "<tablename>_<colname>" could match
    inappropriately when targeting in a result
    set row.  [ticket:2377]

  - [bug] Fixed bug in "mock" strategy whereby
    correct DDL visit method wasn't called, resulting
    in "CREATE/DROP SEQUENCE" statements being
    duplicated [ticket:2384]

- sqlite
  - [bug] the "name" of an FK constraint in SQLite
    is reflected as "None", not "0" or other
    integer value [ticket:2364].
    SQLite does not appear to support constraint
    naming in any case.

  - [bug] sql.false() and sql.true() compile to
    0 and 1, respectively in sqlite [ticket:2368]

  - [bug] removed an erroneous "raise" in the
    SQLite dialect when getting table names
    and view names, where logic is in place
    to fall back to an older version of
    SQLite that doesn't have the
    "sqlite_temp_master" table.

- mysql
  - [bug] fixed regexp that filters out warnings
    for non-reflected "PARTITION" directives,
    thanks to George Reilly [ticket:2376]

- mssql
  - [bug] Adjusted the regexp used in the
    mssql.TIME type to ensure only six digits
    are received for the "microseconds" portion
    of the value, which is expected by
    Python's datetime.time().  Note that
    support for sending microseconds doesn't
    seem to be possible yet with pyodbc
    at least.  [ticket:2340]

  - [bug] Dropped the "30 char" limit on pymssql,
    based on reports that it's doing things
    better these days.  pymssql hasn't been
    well tested and as the DBAPI is in flux
    it's still not clear what the status
    is on this driver and how SQLAlchemy's
    implementation should adapt.  [ticket:2347]

- oracle
  - [bug] Added ORA-03135 to the never ending
    list of oracle "connection lost" errors
    [ticket:2388]

- core
  - [bug] Changed LRUCache, used by the mapper
    to cache INSERT/UPDATE/DELETE statements,
    to use an incrementing counter instead
    of a timestamp to track entries, for greater
    reliability versus using time.time(), which
    can cause test failures on some platforms.
    [ticket:2379]

  - [bug] Added a boolean check for the "finalize"
    function within the pool connection proxy's
    weakref callback before calling it, so that a
    warning isn't emitted that this function is None
    when the application is exiting and gc has
    removed the function from the module before the
    weakref callback was invoked.  [ticket:2383]

- Py3K
  - [bug] Fixed inappropriate usage of util.py3k
    flag and renamed it to util.py3k_warning, since
    this flag is intended to detect the -3 flag
    series of import restrictions only.
    [ticket:2348]

- examples
  - [feature] Simplified the versioning example
    a bit to use a declarative mixin as well
    as an event listener, instead of a metaclass +
    SessionExtension.  [ticket:2313]

  - [bug] Fixed large_collection.py to close the
    session before dropping tables. [ticket:2346]

0.7.4 (December 9, 2011)
=====
- orm
  - [bug] Fixed backref behavior when "popping" the
    value off of a many-to-one in response to
    a removal from a stale one-to-many - the operation
    is skipped, since the many-to-one has since
    been updated.  [ticket:2315]

  - [bug] After some years of not doing this, added
    more granularity to the "is X a parent of Y"
    functionality, which is used when determining
    if the FK on "Y" needs to be "nulled out" as well
    as if "Y" should be deleted with delete-orphan
    cascade.   The test now takes into account the
    Python identity of the parent as well its identity
    key, to see if the last known parent of Y is
    definitely X.   If a decision
    can't be made, a StaleDataError is raised.  The
    conditions where this error is raised are fairly
    rare, requiring that the previous parent was
    garbage collected, and previously
    could very well inappropriately update/delete
    a record that's since moved onto a new parent,
    though there may be some cases where
    "silent success" occurred previously that will now
    raise in the face of ambiguity.
    Expiring "Y" resets the "parent" tracker, meaning
    X.remove(Y) could then end up deleting Y even
    if X is stale, but this is the same behavior
    as before; it's advised to expire X also in that
    case.  [ticket:2264]

  - [bug] fixed inappropriate evaluation of user-mapped
    object in a boolean context within query.get()
    [ticket:2310].  Also in 0.6.9.

  - [bug] Added missing comma to PASSIVE_RETURN_NEVER_SET
    symbol [ticket:2304]

  - [bug] Cls.column.collate("some collation") now
    works.  [ticket:1776]  Also in 0.6.9

  - [bug] the value of a composite attribute is now
    expired after an insert or update operation, instead
    of regenerated in place.  This ensures that a
    column value which is expired within a flush
    will be loaded first, before the composite
    is regenerated using that value.  [ticket:2309]

  - [bug] The fix in [ticket:2309] also emits the
    "refresh" event when the composite value is
    loaded on access, even if all column
    values were already present, as is appropriate.
    This fixes the "mutable" extension which relies
    upon the "load" event to ensure the _parents
    dictionary is up to date, fixes [ticket:2308].
    Thanks to Scott Torborg for the test case here.

  - [bug] Fixed bug whereby a subclass of a subclass
    using concrete inheritance in conjunction with
    the new ConcreteBase or AbstractConcreteBase
    would fail to apply the subclasses deeper than
    one level to the "polymorphic loader" of each
    base  [ticket:2312]

  - [bug] Fixed bug whereby a subclass of a subclass
    using the new AbstractConcreteBase would fail
    to acquire the correct "base_mapper" attribute
    when the "base" mapper was generated, thereby
    causing failures later on.  [ticket:2312]

  - [bug] Fixed bug whereby column_property() created
    against ORM-level column could be treated as
    a distinct entity when producing certain
    kinds of joined-inh joins.  [ticket:2316]

  - [bug] Fixed the error formatting raised when
    a tuple is inadvertently passed to session.query()
    [ticket:2297].  Also in 0.6.9.

  - [bug] Calls to query.join() to a single-table
    inheritance subclass are now tracked, and
    are used to eliminate the additional WHERE..
    IN criterion normally tacked on with single
    table inheritance, since the join should
    accommodate it.  This allows OUTER JOIN
    to a single table subclass to produce
    the correct results, and overall will produce
    fewer WHERE criterion when dealing with
    single table inheritance joins.
    [ticket:2328]

  - [bug] __table_args__ can now be passed as
    an empty tuple as well as an empty dict.
    [ticket:2339].  Thanks to Fayaz Yusuf Khan
    for the patch.

  - [bug] Updated warning message when setting
    delete-orphan without delete to no longer
    refer to 0.6, as we never got around to
    upgrading this to an exception.  Ideally
    this might be better as an exception but
    it's not critical either way.  [ticket:2325]

  - [feature] polymorphic_on now accepts many
    new kinds of values:

      - standalone expressions that aren't
        otherwise mapped
      - column_property() objects
      - string names of any column_property()
        or attribute name of a mapped Column

    The docs include an example using
    the case() construct, which is likely to be
    a common constructed used here.
    [ticket:2345] and part of [ticket:2238]

    Standalone expressions in polymorphic_on
    propagate to single-table inheritance
    subclasses so that they are used in the
    WHERE /JOIN clause to limit rows to that
    subclass as is the usual behavior.

  - [feature] IdentitySet supports the - operator
    as the same as difference(), handy when dealing
    with Session.dirty etc. [ticket:2301]

  - [feature] Added new value for Column autoincrement
    called "ignore_fk", can be used to force autoincrement
    on a column that's still part of a ForeignKeyConstraint.
    New example in the relationship docs illustrates
    its use.

  - [bug] Fixed bug in get_history() when referring
    to a composite attribute that has no value;
    added coverage for get_history() regarding
    composites which is otherwise just a userland
    function.

- sql
   - [bug] related to [ticket:2316], made some
     adjustments to the change from [ticket:2261]
     regarding the "from" list on a select(). The
     _froms collection is no longer memoized, as this
     simplifies various use cases and removes the
     need for a "warning" if a column is attached
     to a table after it was already used in an
     expression - the select() construct will now
     always produce the correct expression.
     There's probably no real-world
     performance hit here; select() objects are
     almost always made ad-hoc, and systems that
     wish to optimize the re-use of a select()
     would be using the "compiled_cache" feature.
     A hit which would occur when calling select.bind
     has been reduced, but the vast majority
     of users shouldn't be using "bound metadata"
     anyway :).

   - [feature] The update() construct can now accommodate
     multiple tables in the WHERE clause, which will
     render an "UPDATE..FROM" construct, recognized by
     Postgresql and MSSQL.  When compiled on MySQL,
     will instead generate "UPDATE t1, t2, ..".  MySQL
     additionally can render against multiple tables in the
     SET clause, if Column objects are used as keys
     in the "values" parameter or generative method.
     [ticket:2166] [ticket:1944]

   - [feature] Added accessor to types called "python_type",
     returns the rudimentary Python type object
     for a particular TypeEngine instance, if known,
     else raises NotImplementedError.  [ticket:77]

   - [bug] further tweak to the fix from [ticket:2261],
     so that generative methods work a bit better
     off of cloned (this is almost a non-use case though).
     In particular this allows with_only_columns()
     to behave more consistently.   Added additional
     documentation to with_only_columns() to clarify
     expected behavior, which changed as a result
     of [ticket:2261].  [ticket:2319]

- engine
  - [bug] Fixed bug whereby transaction.rollback()
    would throw an error on an invalidated
    connection if the transaction were a
    two-phase or savepoint transaction.
    For plain transactions, rollback() is a no-op
    if the connection is invalidated, so while
    it wasn't 100% clear if it should be a no-op,
    at least now the interface is consistent.
    [ticket:2317]

- schema
  - [feature] Added new support for remote "schemas":
    - MetaData() accepts "schema" and "quote_schema"
      arguments, which will be applied to the same-named
      arguments of a Table
      or Sequence which leaves these at their default
      of ``None``.
    - Sequence accepts "quote_schema" argument
    - tometadata() for Table will use the "schema"
      of the incoming MetaData for the new Table
      if the schema argument is explicitly "None"
    - Added CreateSchema and DropSchema DDL
      constructs - these accept just the string
      name of a schema and a "quote" flag.
    - When using default "schema" with MetaData,
      ForeignKey will also assume the "default" schema
      when locating remote table.  This allows the "schema"
      argument on MetaData to be applied to any
      set of Table objects that otherwise don't have
      a "schema".
    - a "has_schema" method has been implemented
      on dialect, but only works on Postgresql so far.
    Courtesy Manlio Perillo, [ticket:1679]

  - [feature] The "extend_existing" flag on Table
    now allows for the reflection process to take
    effect for a Table object that's already been
    defined; when autoload=True and extend_existing=True
    are both set, the full set of columns will be
    reflected from the Table which will then
    *overwrite* those columns already present,
    rather than no activity occurring.  Columns that
    are present directly in the autoload run
    will be used as always, however.
    [ticket:1410]

  - [bug] Fixed bug whereby TypeDecorator would
    return a stale value for _type_affinity, when
    using a TypeDecorator that "switches" types,
    like the CHAR/UUID type.

  - [bug] Fixed bug whereby "order_by='foreign_key'"
    option to Inspector.get_table_names
    wasn't implementing the sort properly, replaced
    with the existing sort algorithm

  - [bug] the "name" of a column-level CHECK constraint,
    if present, is now rendered in the CREATE TABLE
    statement using "CONSTRAINT <name> CHECK <expression>".
    [ticket:2305]

- pyodbc
   - [bug] pyodbc-based dialects now parse the
     pyodbc accurately as far as observed
     pyodbc strings, including such gems
     as "py3-3.0.1-beta4" [ticket:2318]

- postgresql
   - [bug] Postgresql dialect memoizes that an ENUM of a
     particular name was processed
     during a create/drop sequence.  This allows
     a create/drop sequence to work without any
     calls to "checkfirst", and also means with
     "checkfirst" turned on it only needs to
     check for the ENUM once.  [ticket:2311]

   - [feature] Added create_type constructor argument
     to pg.ENUM.  When False, no CREATE/DROP or
     checking for the type will be performed as part
     of a table create/drop event; only the
     create()/drop)() methods called directly
     will do this.  Helps with Alembic "offline"
     scripts.

- mssql
  - [feature] lifted the restriction on SAVEPOINT
    for SQL Server.  All tests pass using it,
    it's not known if there are deeper issues
    however.   [ticket:822]

  - [bug] repaired the with_hint() feature which
    wasn't implemented correctly on MSSQL -
    usually used for the "WITH (NOLOCK)" hint
    (which you shouldn't be using anyway !
    use snapshot isolation instead :) )
    [ticket:2336]

  - [bug] use new pyodbc version detection for
    _need_decimal_fix option, [ticket:2318]

  - [bug] don't cast "table name" as NVARCHAR
    on SQL Server 2000.  Still mostly in the dark
    what incantations are needed to make PyODBC
    work fully with FreeTDS 0.91 here, however.
    [ticket:2343]

  - [bug] Decode incoming values when retrieving
    list of index names and the names of columns
    within those indexes.  [ticket:2269]

- mysql
  - [bug] Unicode adjustments allow latest pymysql
    (post 0.4) to pass 100% on Python 2.

- ext
   - [feature] Added an example to the hybrid docs
     of a "transformer" - a hybrid that returns a
     query-transforming callable in combination
     with a custom comparator.   Uses a new method
     on Query called with_transformation().  The use
     case here is fairly experimental, but only
     adds one line of code to Query.

   - [bug] the @compiles decorator raises an
     informative error message when no "default"
     compilation handler is present, rather
     than KeyError.

- examples
   - [bug] Fixed bug in history_meta.py example where
     the "unique" flag was not removed from a
     single-table-inheritance subclass which
     generates columns to put up onto the base.

0.7.3
=====
- general
   - Adjusted the "importlater" mechanism, which is
     used internally to resolve import cycles,
     such that the usage of __import__ is completed
     when the import of sqlalchemy or sqlalchemy.orm
     is done, thereby avoiding any usage of __import__
     after the application starts new threads,
     fixes [ticket:2279].  Also in 0.6.9.

- orm
   - Improved query.join() such that the "left" side
     can more flexibly be a non-ORM selectable,
     such as a subquery.   A selectable placed
     in select_from() will now be used as the left
     side, favored over implicit usage
     of a mapped entity.
     If the join still fails based on lack of
     foreign keys, the error message includes
     this detail.  Thanks to brianrhude
     on IRC for the test case.  [ticket:2298]

   - Added after_soft_rollback() Session event.  This
     event fires unconditionally whenever rollback()
     is called, regardless of if an actual DBAPI
     level rollback occurred.  This event
     is specifically designed to allow operations
     with the Session to proceed after a rollback
     when the Session.is_active is True.
     [ticket:2241]

  - added "adapt_on_names" boolean flag to orm.aliased()
    construct.  Allows an aliased() construct
    to link the ORM entity to a selectable that contains
    aggregates or other derived forms of a particular
    attribute, provided the name is the same as that
    of the entity mapped column.

  - Added new flag expire_on_flush=False to column_property(),
    marks those properties that would otherwise be considered
    to be "readonly", i.e. derived from SQL expressions,
    to retain their value after a flush has occurred, including
    if the parent object itself was involved in an update.

  - Enhanced the instrumentation in the ORM to support
    Py3K's new argument style of "required kw arguments",
    i.e. fn(a, b, *, c, d), fn(a, b, *args, c, d).
    Argument signatures of mapped object's __init__
    method will be preserved, including required kw rules.
    [ticket:2237]

  - Fixed bug in unit of work whereby detection of
    "cycles" among classes in highly interlinked patterns
    would not produce a deterministic
    result; thereby sometimes missing some nodes that
    should be considered cycles and causing further
    issues down the road.  Note this bug is in 0.6
    also; not backported at the moment.
    [ticket:2282]

  - Fixed a variety of synonym()-related regressions
    from 0.6:
        - making a synonym against a synonym now works.
        - synonyms made against a relationship() can
          be passed to query.join(), options sent
          to query.options(), passed by name
          to query.with_parent().

  - Fixed bug whereby mapper.order_by attribute would
    be ignored in the "inner" query within a
    subquery eager load.  [ticket:2287].
    Also in 0.6.9.

  - Identity map .discard() uses dict.pop(,None)
    internally instead of "del" to avoid KeyError/warning
    during a non-determinate gc teardown [ticket:2267]

  - Fixed regression in new composite rewrite where
    deferred=True option failed due to missing
    import [ticket:2253]

  - Reinstated "comparator_factory" argument to
    composite(), removed when 0.7 was released.
    [ticket:2248]

  - Fixed bug in query.join() which would occur
    in a complex multiple-overlapping path scenario,
    where the same table could be joined to
    twice.  Thanks *much* to Dave Vitek
    for the excellent fix here.  [ticket:2247]

  - Query will convert an OFFSET of zero when
    slicing into None, so that needless OFFSET
    clauses are not invoked.

  - Repaired edge case where mapper would fail
    to fully update internal state when a relationship
    on a new mapper would establish a backref on the
    first mapper.

  - Fixed bug whereby if __eq__() was
    redefined, a relationship many-to-one lazyload
    would hit the __eq__() and fail.  [ticket:2260]
    Does not apply to 0.6.9.

  - Calling class_mapper() and passing in an object
    that is not a "type" (i.e. a class that could
    potentially be mapped) now raises an informative
    ArgumentError, rather than UnmappedClassError.
    [ticket:2196]

  - New event hook, MapperEvents.after_configured().
    Called after a configure() step has completed and
    mappers were in fact affected.   Theoretically this
    event is called once per application, unless new mappings
    are constructed after existing ones have been used
    already.

  - When an open Session is garbage collected, the objects
    within it which remain are considered detached again
    when they are add()-ed to a new Session.
    This is accomplished by an extra check that the previous
    "session_key" doesn't actually exist among the pool
    of Sessions.  [ticket:2281]

  - New declarative features:
        - __declare_last__() method, establishes an event
        listener for the class method that will be called
        when mappers are completed with the final "configure"
        step.
        - __abstract__ flag.   The class will not be mapped
        at all when this flag is present on the class.
        - New helper classes ConcreteBase, AbstractConcreteBase.
        Allow concrete mappings using declarative which automatically
        set up the "polymorphic_union" when the "configure"
        mapper step is invoked.
        - The mapper itself has semi-private methods that allow
        the "with_polymorphic" selectable to be assigned
        to the mapper after it has already been configured.
        [ticket:2239]

   - Declarative will warn when a subclass' base uses
     @declared_attr for a regular column - this attribute
     does not propagate to subclasses. [ticket:2283]

   - The integer "id" used to link a mapped instance with
     its owning Session is now generated by a sequence
     generation function rather than id(Session), to
     eliminate the possibility of recycled id() values
     causing an incorrect result, no need to check that
     object actually in the session.  [ticket:2280]

-sql
  - Behavioral improvement: empty
    conjunctions such as and_() and or_() will be
    flattened in the context of an enclosing conjunction,
    i.e. and_(x, or_()) will produce 'X' and not 'X AND
    ()'. [ticket:2257].

  - Fixed bug regarding calculation of "from" list
    for a select() element.  The "from" calc is now
    delayed, so that if the construct uses a Column
    object that is not yet attached to a Table,
    but is later associated with a Table, it generates
    SQL using the table as a FROM.   This change
    impacted fairly deeply the mechanics of how
    the FROM list as well as the "correlates" collection
    is calculated, as some "clause adaption" schemes
    (these are used very heavily in the ORM)
    were relying upon the fact that the "froms"
    collection would typically be cached before the
    adaption completed.   The rework allows it
    such that the "froms" collection can be cleared
    and re-generated at any time.  [ticket:2261]

  - Fixed bug whereby with_only_columns() method of
    Select would fail if a selectable were passed.
    [ticket:2270].  Also in 0.6.9.

- schema
  - Modified Column.copy() to use _constructor(),
    which defaults to self.__class__, in order to
    create the new object.  This allows easier support
    of subclassing Column.  [ticket:2284]

  - Added a slightly nicer __repr__() to SchemaItem
    classes.  Note the repr here can't fully support
    the "repr is the constructor" idea since schema
    items can be very deeply nested/cyclical, have
    late initialization of some things, etc.
    [ticket:2223]

- engine
  - The recreate() method in all pool classes uses
    self.__class__ to get at the type of pool
    to produce, in the case of subclassing.  Note
    there's no usual need to subclass pools.
    [ticket:2254]

  - Improvement to multi-param statement logging,
    long lists of bound parameter sets will be
    compressed with an informative indicator
    of the compression taking place.  Exception
    messages use the same improved formatting.
    [ticket:2243]

  - Added optional "sa_pool_key" argument to
    pool.manage(dbapi).connect() so that serialization
    of args is not necessary.

  - The entry point resolution supported by
    create_engine() now supports resolution of
    individual DBAPI drivers on top of a built-in
    or entry point-resolved dialect, using the
    standard '+' notation - it's converted to
    a '.' before being resolved as an entry
    point.  [ticket:2286]

  - Added an exception catch + warning for the
    "return unicode detection" step within connect,
    allows databases that crash on NVARCHAR to
    continue initializing, assuming no NVARCHAR
    type implemented.  [ticket:2299]

- types
  - Extra keyword arguments to the base Float
    type beyond "precision" and "asdecimal" are ignored;
    added a deprecation warning here and additional
    docs, related to [ticket:2258]

- sqlite
  - Ensured that the same ValueError is raised for
    illegal date/time/datetime string parsed from
    the database regardless of whether C
    extensions are in use or not.

- postgresql
  - Added "postgresql_using" argument to Index(), produces
    USING clause to specify index implementation for
    PG.  [ticket:2290].  Thanks to Ryan P. Kelly for
    the patch.

  - Added client_encoding parameter to create_engine()
    when the postgresql+psycopg2 dialect is used;
    calls the psycopg2 set_client_encoding() method
    with the value upon connect.  [ticket:1839]

  - Fixed bug related to [ticket:2141] whereby the
    same modified index behavior in PG 9 affected
    primary key reflection on a renamed column.
    [ticket:2291].  Also in 0.6.9.

  - Reflection functions for Table, Sequence no longer
    case insensitive.  Names can be differ only in case
    and will be correctly distinguished.  [ticket:2256]

  - Use an atomic counter as the "random number"
    source for server side cursor names;
    conflicts have been reported in rare cases.

  - Narrowed the assumption made when reflecting
    a foreign-key referenced table with schema in
    the current search path; an explicit schema will
    be applied to the referenced table only if
    it actually matches that of the referencing table,
    which also has an explicit schema.   Previously
    it was assumed that "current" schema was synonymous
    with the full search_path.  [ticket:2249]

- mysql
  - a CREATE TABLE will put the COLLATE option
    after CHARSET, which appears to be part of
    MySQL's arbitrary rules regarding if it will actually
    work or not.  [ticket:2225]  Also in 0.6.9.

  - Added mysql_length parameter to Index construct,
    specifies "length" for indexes.  [ticket:2293]

- mssql
  - Changes to attempt support of FreeTDS 0.91 with
    Pyodbc.  This includes that string binds are sent as
    Python unicode objects when FreeTDS 0.91 is detected,
    and a CAST(? AS NVARCHAR) is used when we detect
    for a table.   However, I'd continue
    to characterize Pyodbc + FreeTDS 0.91 behavior as
    pretty crappy, there are still many queries such
    as used in reflection which cause a core dump on
    Linux, and it is not really usable at all
    on OSX, MemoryErrors abound and just plain broken
    unicode support.   [ticket:2273]

  - The behavior of =/!= when comparing a scalar select
    to a value will no longer produce IN/NOT IN as of 0.8;
    this behavior is a little too heavy handed (use in_() if
    you want to emit IN) and now emits a deprecation warning.
    To get the 0.8 behavior immediately and remove the warning,
    a compiler recipe is given at
    http://www.sqlalchemy.org/docs/07/dialects/mssql.html#scalar-select-comparisons
    to override the behavior of visit_binary().
    [ticket:2277]

  - "0" is accepted as an argument for limit() which
    will produce "TOP 0". [ticket:2222]

- oracle
  - Fixed ReturningResultProxy for zxjdbc dialect.
    [ticket:2272].  Regression from 0.6.

  - The String type now generates VARCHAR2 on Oracle
    which is recommended as the default VARCHAR.
    Added an explicit VARCHAR2 and NVARCHAR2 to the Oracle
    dialect as well.   Using NVARCHAR still generates
    "NVARCHAR2" - there is no "NVARCHAR" on Oracle -
    this remains a slight breakage of the "uppercase types
    always give exactly that" policy.  VARCHAR still
    generates "VARCHAR", keeping with the policy.   If
    Oracle were to ever define "VARCHAR" as something
    different as they claim (IMHO this will never happen),
    the type would be available.  [ticket:2252]

- ext
  - SQLSoup will not be included in version 0.8
    of SQLAlchemy; while useful, we would like to
    keep SQLAlchemy itself focused on one ORM
    usage paradigm.  SQLSoup will hopefully
    soon be superseded by a third party
    project.  [ticket:2262]

  - Added local_attr, remote_attr, attr accessors
    to AssociationProxy, providing quick access
    to the proxied attributes at the class
    level. [ticket:2236]

  - Changed the update() method on association proxy
    dictionary to use a duck typing approach, i.e.
    checks for "keys", to discern between update({})
    and update((a, b)).   Previously, passing a
    dictionary that had tuples as keys would be misinterpreted
    as a sequence. [ticket:2275]

- examples
  - Adjusted dictlike-polymorphic.py example
    to apply the CAST such that it works on
    PG, other databases.  [ticket:2266]
    Also in 0.6.9.

0.7.2
=====
- orm
  - Feature enhancement: joined and subquery
    loading will now traverse already-present related
    objects and collections in search of unpopulated
    attributes throughout the scope of the eager load
    being defined, so that the eager loading that is
    specified via mappings or query options
    unconditionally takes place for the full depth,
    populating whatever is not already populated.
    Previously, this traversal would stop if a related
    object or collection were already present leading
    to inconsistent behavior (though would save on
    loads/cycles for an already-loaded graph). For a
    subqueryload, this means that the additional
    SELECT statements emitted by subqueryload will
    invoke unconditionally, no matter how much of the
    existing graph is already present (hence the
    controversy). The previous behavior of "stopping"
    is still in effect when a query is the result of
    an attribute-initiated lazyload, as otherwise an
    "N+1" style of collection iteration can become
    needlessly expensive when the same related object
    is encountered repeatedly. There's also an
    as-yet-not-public generative Query method
    _with_invoke_all_eagers()
    which selects old/new behavior [ticket:2213]

  - A rework of "replacement traversal" within
    the ORM as it alters selectables to be against
    aliases of things (i.e. clause adaption) includes
    a fix for multiply-nested any()/has() constructs
    against a joined table structure.  [ticket:2195]

  - Fixed bug where query.join() + aliased=True
    from a joined-inh structure to itself on
    relationship() with join condition on the child
    table would convert the lead entity into the
    joined one inappropriately.  [ticket:2234]
    Also in 0.6.9.

  - Fixed regression from 0.6 where Session.add()
    against an object which contained None in a
    collection would raise an internal exception.
    Reverted this to 0.6's behavior which is to
    accept the None but obviously nothing is
    persisted.  Ideally, collections with None
    present or on append() should at least emit a
    warning, which is being considered for 0.8.
    [ticket:2205]

  - Load of a deferred() attribute on an object
    where row can't be located raises
    ObjectDeletedError instead of failing later
    on; improved the message in ObjectDeletedError
    to include other conditions besides a simple
    "delete". [ticket:2191]

  - Fixed regression from 0.6 where a get history
    operation on some relationship() based attributes
    would fail when a lazyload would emit; this could
    trigger within a flush() under certain conditions.
    [ticket:2224]  Thanks to the user who submitted
    the great test for this.

  - Fixed bug apparent only in Python 3 whereby
    sorting of persistent + pending objects during
    flush would produce an illegal comparison,
    if the persistent object primary key
    is not a single integer.  [ticket:2228]
    Also in 0.6.9

  - Fixed bug whereby the source clause
    used by query.join() would be inconsistent
    if against a column expression that combined
    multiple entities together.  [ticket:2197]
    Also in 0.6.9

  - Fixed bug whereby if a mapped class
    redefined __hash__() or __eq__() to something
    non-standard, which is a supported use case
    as SQLA should never consult these,
    the methods would be consulted if the class
    was part of a "composite" (i.e. non-single-entity)
    result set.  [ticket:2215]
    Also in 0.6.9.

  - Added public attribute ".validators" to
    Mapper, an immutable dictionary view of
    all attributes that have been decorated
    with the @validates decorator.
    [ticket:2240] courtesy Stefano Fontanelli

  - Fixed subtle bug that caused SQL to blow
    up if: column_property() against subquery +
    joinedload + LIMIT + order by the column
    property() occurred.  [ticket:2188].
    Also in 0.6.9

  - The join condition produced by with_parent
    as well as when using a "dynamic" relationship
    against a parent will generate unique
    bindparams, rather than incorrectly repeating
    the same bindparam.  [ticket:2207].
    Also in 0.6.9.

  - Added the same "columns-only" check to
    mapper.polymorphic_on as used when
    receiving user arguments to
    relationship.order_by, foreign_keys,
    remote_side, etc.

  - Fixed bug whereby comparison of column
    expression to a Query() would not call
    as_scalar() on the underlying SELECT
    statement to produce a scalar subquery,
    in the way that occurs if you called
    it on Query().subquery(). [ticket:2190]

  - Fixed declarative bug where a class inheriting
    from a superclass of the same name would fail
    due to an unnecessary lookup of the name
    in the _decl_class_registry. [ticket:2194]

  - Repaired the "no statement condition"
    assertion in Query which would attempt
    to raise if a generative method were called
    after from_statement() were called.
    [ticket:2199].  Also in 0.6.9.

- sql
  - Fixed two subtle bugs involving column
    correspondence in a selectable,
    one with the same labeled subquery repeated, the other
    when the label has been "grouped" and
    loses itself.  Affects [ticket:2188].

- schema
  - New feature: with_variant() method on
    all types.  Produces an instance of Variant(),
    a special TypeDecorator which will select
    the usage of a different type based on the
    dialect in use. [ticket:2187]

  - Added an informative error message when
    ForeignKeyConstraint refers to a column name in
    the parent that is not found.  Also in 0.6.9.

  - Fixed bug whereby adaptation of old append_ddl_listener()
    function was passing unexpected **kw through
    to the Table event.   Table gets no kws, the MetaData
    event in 0.6 would get "tables=somecollection",
    this behavior is preserved.  [ticket:2206]

  - Fixed bug where "autoincrement" detection on
    Table would fail if the type had no "affinity"
    value, in particular this would occur when using
    the UUID example on the site that uses TypeEngine
    as the "impl".

  - Added an improved repr() to TypeEngine objects
    that will only display constructor args which
    are positional or kwargs that deviate
    from the default.  [ticket:2209]

- engine
  - Context manager provided by Connection.begin()
    will issue rollback() if the commit() fails,
    not just if an exception occurs.

  - Use urllib.parse_qsl() in Python 2.6 and above,
    no deprecation warning about cgi.parse_qsl()
    [ticket:1682]

  - Added mixin class sqlalchemy.ext.DontWrapMixin.
    User-defined exceptions of this type are never
    wrapped in StatementException when they
    occur in the context of a statement
    execution.

  - StatementException wrapping will display the
    original exception class in the message.

  - Failures on connect which raise dbapi.Error
    will forward the error to dialect.is_disconnect()
    and set the "connection_invalidated" flag if
    the dialect knows this to be a potentially
    "retryable" condition.  Only Oracle ORA-01033
    implemented for now.  [ticket:2201]

- sqlite
  - SQLite dialect no longer strips quotes
    off of reflected default value, allowing
    a round trip CREATE TABLE to work.
    This is consistent with other dialects
    that also maintain the exact form of
    the default.  [ticket:2189]

- postgresql
  - Added new "postgresql_ops" argument to
    Index, allows specification of PostgreSQL
    operator classes for indexed columns.
    [ticket:2198]  Courtesy Filip Zyzniewski.

- mysql
  - Fixed OurSQL dialect to use ansi-neutral
    quote symbol "'" for XA commands instead
    of '"'.  [ticket:2186].  Also in 0.6.9.

- mssql
  - Adjusted the pyodbc dialect such that bound
    values are passed as bytes and not unicode
    if the "Easysoft" unix drivers are detected.
    This is the same behavior as occurs with
    FreeTDS.  Easysoft appears to segfault
    if Python unicodes are passed under
    certain circumstances.

- oracle
  - Added ORA-00028 to disconnect codes, use
    cx_oracle _Error.code to get at the code,
    [ticket:2200].  Also in 0.6.9.

  - Added ORA-01033 to disconnect codes, which
    can be caught during a connection
    event.  [ticket:2201]

  - repaired the oracle.RAW type which did not
    generate the correct DDL.  [ticket:2220]
    Also in 0.6.9.

  - added CURRENT to reserved word list.
    [ticket:2212] Also in 0.6.9.

-ext
  - Fixed bug in the mutable extension whereby
    if the same type were used twice in one
    mapping, the attributes beyond the first
    would not get instrumented.

  - Fixed bug in the mutable extension whereby
    if None or a non-corresponding type were set,
    an error would be raised.  None is now accepted
    which assigns None to all attributes,
    illegal values raise ValueError.

- examples
  - Repaired the examples/versioning test runner
    to not rely upon SQLAlchemy test libs,
    nosetests must be run from within
    examples/versioning to get around setup.cfg
    breaking it.

  - Tweak to examples/versioning to pick the
    correct foreign key in a multi-level
    inheritance situation.

  - Fixed the attribute shard example to check
    for bind param callable correctly in 0.7
    style.

0.7.1
=====
- general
  - Added a workaround for Python bug 7511 where
    failure of C extension build does not
    raise an appropriate exception on Windows 64
    bit + VC express [ticket:2184]

- orm
  - "delete-orphan" cascade is now allowed on
    self-referential relationships - this since
    SQLA 0.7 no longer enforces "parent with no
    child" at the ORM level; this check is left
    up to foreign key nullability.
    Related to [ticket:1912]

  - Repaired new "mutable" extension to propagate
    events to subclasses correctly; don't
    create multiple event listeners for
    subclasses either.  [ticket:2180]

  - Modify the text of the message which occurs
    when the "identity" key isn't detected on
    flush, to include the common cause that
    the Column isn't set up to detect
    auto-increment correctly; [ticket:2170].
    Also in 0.6.8.

  - Fixed bug where transaction-level "deleted"
    collection wouldn't be cleared of expunged
    states, raising an error if they later
    became transient [ticket:2182].
    Also in 0.6.8.

- sql
  - Fixed bug whereby metadata.reflect(bind)
    would close a Connection passed as a
    bind argument.  Regression from 0.6.

  - Streamlined the process by which a Select
    determines what's in it's '.c' collection.
    Behaves identically, except that a
    raw ClauseList() passed to select([])
    (which is not a documented case anyway) will
    now be expanded into its individual column
    elements instead of being ignored.

- engine
  - Deprecate schema/SQL-oriented methods on
    Connection/Engine that were never well known
    and are redundant:  reflecttable(), create(),
    drop(), text(), engine.func

  - Adjusted the __contains__() method of
    a RowProxy result row such that no exception
    throw is generated internally;
    NoSuchColumnError() also will generate its
    message regardless of whether or not the column
    construct can be coerced to a string.
    [ticket:2178].  Also in 0.6.8.

- sqlite
  - Accept None from cursor.fetchone() when
    "PRAGMA read_uncommitted" is called to determine
    current isolation mode at connect time and
    default to SERIALIZABLE; this to support SQLite
    versions pre-3.3.0 that did not have this
    feature.  [ticket:2173]

- postgresql
  - Some unit test fixes regarding numeric arrays,
    MATCH operator.   A potential floating-point
    inaccuracy issue was fixed, and certain tests
    of the MATCH operator only execute within an
    EN-oriented locale for now.  [ticket:2175].
    Also in 0.6.8.

- mysql
  - Unit tests pass 100% on MySQL installed
    on windows.

  - Removed the "adjust casing" step that would
    fail when reflecting a table on MySQL
    on windows with a mixed case name.  After some
    experimenting with a windows MySQL server, it's
    been determined that this step wasn't really
    helping the situation much; MySQL does not return
    FK names with proper casing on non-windows
    platforms either, and removing the step at
    least allows the reflection to act more like
    it does on other OSes.   A warning here
    has been considered but its difficult to
    determine under what conditions such a warning
    can be raised, so punted on that for now -
    added some docs instead. [ticket:2181]

  - supports_sane_rowcount will be set to False
    if using MySQLdb and the DBAPI doesn't provide
    the constants.CLIENT module.

0.7.0
=======
- This section documents those changes from 0.7b4
  to 0.7.0.  For an overview of what's new in
  SQLAlchemy 0.7, see
  http://www.sqlalchemy.org/trac/wiki/07Migration

- orm
  - Fixed regression introduced in 0.7b4 (!) whereby
    query.options(someoption("nonexistent name")) would
    fail to raise an error.  Also added additional
    error catching for cases where the option would
    try to build off a column-based element, further
    fixed up some of the error messages tailored
    in [ticket:2069]

  - query.count() emits "count(*)" instead of
    "count(1)".  [ticket:2162]

  - Fine tuning of Query clause adaptation when
    from_self(), union(), or other "select from
    myself" operation, such that plain SQL expression
    elements added to filter(), order_by() etc.
    which are present in the nested "from myself"
    query *will* be adapted in the same way an ORM
    expression element will, since these
    elements are otherwise not easily accessible.
    [ticket:2155]

  - Fixed bug where determination of "self referential"
    relationship would fail with no workaround
    for joined-inh subclass related to itself,
    or joined-inh subclass related to a subclass
    of that with no cols in the sub-sub class
    in the join condition.  [ticket:2149]
    Also in 0.6.8.

  - mapper() will ignore non-configured foreign keys
    to unrelated tables when determining inherit
    condition between parent and child class,
    but will raise as usual for unresolved
    columns and table names regarding the inherited
    table.  This is an enhanced generalization of
    behavior that was already applied to declarative
    previously.  [ticket:2153]   0.6.8 has a more
    conservative version of this which doesn't
    fundamentally alter how join conditions
    are determined.

  - It is an error to call query.get() when the
    given entity is not a single, full class
    entity or mapper (i.e. a column).  This is
    a deprecation warning in 0.6.8.
    [ticket:2144]

  - Fixed a potential KeyError which under some
    circumstances could occur with the identity
    map, part of [ticket:2148]

  - added Query.with_session() method, switches
    Query to use a different session.

  - horizontal shard query should use execution
    options per connection as per [ticket:2131]

  - a non_primary mapper will inherit the _identity_class
    of the primary mapper.  This so that a non_primary
    established against a class that's normally in an
    inheritance mapping will produce results that are
    identity-map compatible with that of the primary
    mapper [ticket:2151] (also in 0.6.8)

  - Fixed the error message emitted for "can't
    execute syncrule for destination column 'q';
    mapper 'X' does not map this column" to
    reference the correct mapper.  [ticket:2163].
    Also in 0.6.8.

  - polymorphic_union() gets a "cast_nulls" option,
    disables the usage of CAST when it renders
    the labeled NULL columns.  [ticket:1502]

  - polymorphic_union() renders the columns in their
    original table order, as according to the first
    table/selectable in the list of polymorphic
    unions in which they appear.  (which is itself
    an unordered mapping unless you pass an OrderedDict).

  - Fixed bug whereby mapper mapped to an anonymous
    alias would fail if logging were used, due to
    unescaped % sign in the alias name.  [ticket:2171]
    Also in 0.6.8.

- sql
  - Fixed bug whereby nesting a label of a select()
    with another label in it would produce incorrect
    exported columns.   Among other things this would
    break an ORM column_property() mapping against
    another column_property().  [ticket:2167].
    Also in 0.6.8

  - Changed the handling in determination of join
    conditions such that foreign key errors are
    only considered between the two given tables.
    That is, t1.join(t2) will report FK errors
    that involve 't1' or 't2', but anything
    involving 't3' will be skipped.   This affects
    join(), as well as ORM relationship and
    inherit condition logic.

  - Some improvements to error handling inside
    of the execute procedure to ensure auto-close
    connections are really closed when very
    unusual DBAPI errors occur.

  - metadata.reflect() and reflection.Inspector()
    had some reliance on GC to close connections
    which were internally procured, fixed this.

  - Added explicit check for when Column .name
    is assigned as blank string [ticket:2140]

  - Fixed bug whereby if FetchedValue was passed
    to column server_onupdate, it would not
    have its parent "column" assigned, added
    test coverage for all column default assignment
    patterns.  [ticket:2147]  also in 0.6.8

- postgresql
  - Fixed the psycopg2_version parsing in the
    psycopg2 dialect.

  - Fixed bug affecting PG 9 whereby index reflection
    would fail if against a column whose name
    had changed.  [ticket:2141].  Also in 0.6.8.

- mssql
  - Fixed bug in MSSQL dialect whereby the aliasing
    applied to a schema-qualified table would leak
    into enclosing select statements [ticket:2169].
    Also in 0.6.8.

- documentation
  - Removed the usage of the "collections.MutableMapping"
    abc from the ext.mutable docs as it was being used
    incorrectly and makes the example more difficult
    to understand in any case.  [ticket:2152]

- examples
  - removed the ancient "polymorphic association"
    examples and replaced with an updated set of
    examples that use declarative mixins,
    "generic_associations".   Each presents an alternative
    table layout.

- ext
  - Fixed bugs in sqlalchemy.ext.mutable extension where
    `None` was not appropriately handled, replacement
    events were not appropriately handled.
    [ticket:2143]

0.7.0b4
=======
- general
  - Changes to the format of CHANGES, this file.
    The format changes have been applied to
    the 0.7 releases.

    - The "-declarative" changes will now be listed
      directly under the "-orm" section, as these
      are closely related.

    - The 0.5 series changes have been moved to
      the file CHANGES_PRE_06 which replaces
      CHANGES_PRE_05.

    - The changelog for 0.6.7 and subsequent within
      the 0.6 series is now listed only in the
      CHANGES file within the 0.6 branch.
      In the 0.7 CHANGES file (i.e. this file), all the
      0.6 changes are listed inline within the 0.7
      section in which they were also applied
      (since all 0.6 changes are in 0.7 as well).
      Changes that apply to an 0.6 version here
      are noted as are if any differences in
      implementation/behavior are present.

- orm
  - Some fixes to "evaulate" and "fetch" evaluation
    when query.update(), query.delete() are called.
    The retrieval of records is done after autoflush
    in all cases, and before update/delete is
    emitted, guarding against unflushed data present
    as well as expired objects failing during
    the evaluation.  [ticket:2122]

  - Reworded the exception raised when a flush
    is attempted of a subclass that is not polymorphic
    against the supertype.  [ticket:2063]

  - Still more wording adjustments when a query option
    can't find the target entity.  Explain that the
    path must be from one of the root entities.

  - Some fixes to the state handling regarding
    backrefs, typically when autoflush=False, where
    the back-referenced collection wouldn't
    properly handle add/removes with no net
    change.  Thanks to Richard Murri for the
    test case + patch.  [ticket:2123]
    (also in 0.6.7).

  - Added checks inside the UOW to detect the unusual
    condition of being asked to UPDATE or DELETE
    on a primary key value that contains NULL
    in it.  [ticket:2127]

  - Some refinements to attribute history.  More
    changes are pending possibly in 0.8, but
    for now history has been modified such that
    scalar history doesn't have a "side effect"
    of populating None for a non-present value.
    This allows a slightly better ability to
    distinguish between a None set and no actual
    change, affects [ticket:2127] as well.

  - a "having" clause would be copied from the
    inside to the outside query if from_self()
    were used; in particular this would break
    an 0.7 style count() query [ticket:2130].
    (also in 0.6.7)

  - the Query.execution_options() method now passes
    those options to the Connection rather than
    the SELECT statement, so that all available
    options including isolation level and
    compiled cache may be used.  [ticket:2131]

- sql
  - The "compiled_cache" execution option now raises
    an error when passed to a SELECT statement
    rather than a Connection.  Previously it was
    being ignored entirely.   We may look into
    having this option work on a per-statement
    level at some point. [ticket:2131]

  - Restored the "catchall" constructor on the base
    TypeEngine class, with a deprecation warning.
    This so that code which does something like
    Integer(11) still succeeds.

  - Fixed regression whereby MetaData() coming
    back from unpickling did not keep track of
    new things it keeps track of now, i.e.
    collection of Sequence objects, list
    of schema names.  [ticket:2104]

  - The limit/offset keywords to select() as well
    as the value passed to select.limit()/offset()
    will be coerced to integer.  [ticket:2116]
    (also in 0.6.7)

  - fixed bug where "from" clause gathering from an
    over() clause would be an itertools.chain() and
    not a list, causing "can only concatenate list"
    TypeError when combined with other clauses.

  - Fixed incorrect usage of "," in over() clause
    being placed between the "partition" and "order by"
    clauses.  [ticket:2134]

  - Before/after attach events for PrimaryKeyConstraint
    now function, tests added for before/after events
    on all constraint types.  [ticket:2105]

  - Added explicit true()/false() constructs to expression
    lib - coercion rules will intercept "False"/"True"
    into these constructs.  In 0.6, the constructs were
    typically converted straight to string, which was
    no longer accepted in 0.7.  [ticket:2117]

- engine
  - The C extension is now enabled by default on CPython
    2.x with a fallback to pure python if it fails to
    compile.  [ticket:2129]

- schema
  - The 'useexisting' flag on Table has been superceded
    by a new pair of flags 'keep_existing' and
    'extend_existing'.   'extend_existing' is equivalent
    to 'useexisting' - the existing Table is returned,
    and additional constructor elements are added.
    With 'keep_existing', the existing Table is returned,
    but additional constructor elements are not added -
    these elements are only applied when the Table
    is newly created.   [ticket:2109]

- types
  - REAL has been added to the core types.  Supported
    by Postgresql, SQL Server, MySQL, SQLite.  Note
    that the SQL Server and MySQL versions, which
    add extra arguments, are also still available
    from those dialects.  [ticket:2081]

-event
  - Added @event.listens_for() decorator, given
    target + event name, applies the decorated
    function as a listener.  [ticket:2106]

- pool
  - AssertionPool now stores the traceback indicating
    where the currently checked out connection was
    acquired; this traceback is reported within
    the assertion raised upon a second concurrent
    checkout; courtesy Gunnlaugur Briem
    [ticket:2103]

  - The "pool.manage" feature doesn't use pickle
    anymore to hash the arguments for each pool.

- sqlite
  - Fixed bug where reflection of foreign key
    created as "REFERENCES <tablename>" without
    col name would fail.  [ticket:2115]
    (also in 0.6.7)

- postgresql
  - Psycopg2 for Python 3 is now supported.

  - Fixed support for precision numerics when using
    pg8000. [ticket:2132]

- oracle
  - Using column names that would require quotes
    for the column itself or for a name-generated
    bind parameter, such as names with special
    characters, underscores, non-ascii characters,
    now properly translate bind parameter keys when
    talking to cx_oracle.  [ticket:2100]  (Also
    in 0.6.7)

  - Oracle dialect adds use_binds_for_limits=False
    create_engine() flag, will render the LIMIT/OFFSET
    values inline instead of as binds, reported to
    modify the execution plan used by Oracle.
    [ticket:2116] (Also in 0.6.7)

- documentation
  - Documented SQLite DATE/TIME/DATETIME types.
    [ticket:2029] (also in 0.6.7)

  - Fixed mutable extension docs to show the
    correct type-association methods.
    [ticket:2118]

0.7.0b3
=======
- general
  - Lots of fixes to unit tests when run under Pypy
    (courtesy Alex Gaynor).

- orm
  - Changed the underlying approach to query.count().
    query.count() is now in all cases exactly:

        query.
            from_self(func.count(literal_column('1'))).
            scalar()

    That is, "select count(1) from (<full query>)".
    This produces a subquery in all cases, but
    vastly simplifies all the guessing count()
    tried to do previously, which would still
    fail in many scenarios particularly when
    joined table inheritance and other joins
    were involved.  If the subquery produced
    for an otherwise very simple count is really
    an issue, use query(func.count()) as an
    optimization.  [ticket:2093]

  - some changes to the identity map regarding
    rare weakref callbacks during iterations.
    The mutex has been removed as it apparently
    can cause a reentrant (i.e. in one thread) deadlock,
    perhaps when gc collects objects at the point of
    iteration in order to gain more memory.  It is hoped
    that "dictionary changed during iteration" will
    be exceedingly rare as iteration methods internally
    acquire the full list of objects in a single values()
    call. Note 0.6.7 has a more conservative fix here
    which still keeps the mutex in place. [ticket:2087]

  - A tweak to the unit of work causes it to order
    the flush along relationship() dependencies even if
    the given objects don't have any inter-attribute
    references in memory, which was the behavior in
    0.5 and earlier, so a flush of Parent/Child with
    only foreign key/primary key set will succeed.
    This while still maintaining 0.6 and above's not
    generating a ton of useless internal dependency
    structures within the flush that don't correspond
    to state actually within the current flush.
    [ticket:2082]

  - Improvements to the error messages emitted when
    querying against column-only entities in conjunction
    with (typically incorrectly) using loader options,
    where the parent entity is not fully present.
    [ticket:2069]

  - Fixed bug in query.options() whereby a path
    applied to a lazyload using string keys could
    overlap a same named attribute on the wrong
    entity.  Note 0.6.7 has a more conservative fix
    to this.  [ticket:2098]

- declarative
  - Arguments in __mapper_args__ that aren't "hashable"
    aren't mistaken for always-hashable, possibly-column
    arguments.  [ticket:2091] (also in 0.6.7)

- sql
  - Added a fully descriptive error message for the
    case where Column is subclassed and _make_proxy()
    fails to make a copy due to TypeError on the
    constructor.   The method _constructor should
    be implemented in this case.

  - Added new event "column_reflect" for Table objects.
    Receives the info dictionary about a Column before
    the object is generated within reflection, and allows
    modification to the dictionary for control over
    most aspects of the resulting Column including
    key, name, type, info dictionary.  [ticket:2095]

  - To help with the "column_reflect" event being used
    with specific Table objects instead of all instances
    of Table, listeners can be added to a Table object
    inline with its construction using a new argument
    "listeners", a list of tuples of the form
    (<eventname>, <fn>), which are applied to the Table
    before the reflection process begins.

  - Added new generic function "next_value()", accepts
    a Sequence object as its argument and renders the
    appropriate "next value" generation string on the
    target platform, if supported.  Also provides
    ".next_value()" method on Sequence itself.
    [ticket:2085]

  - func.next_value() or other SQL expression can
    be embedded directly into an insert() construct,
    and if implicit or explicit "returning" is used
    in conjunction with a primary key column,
    the newly generated value will be present in
    result.inserted_primary_key. [ticket:2084]

  - Added accessors to ResultProxy "returns_rows",
    "is_insert" [ticket:2089] (also in 0.6.7)

- engine
  - Fixed AssertionPool regression bug.  [ticket:2097]

  - Changed exception raised to ArgumentError when an
    invalid dialect is specified. [ticket:2060]

- postgresql
  - Added RESERVED_WORDS for postgresql dialect. [ticket:2092]
    (also in 0.6.7)

  - Fixed the BIT type to allow a "length" parameter, "varying"
    parameter.  Reflection also fixed.  [ticket:2073]
    (also in 0.6.7)

- mssql
  - Rewrote the query used to get the definition of a view,
    typically when using the Inspector interface, to
    use sys.sql_modules instead of the information schema,
    thereby allowing views definitions longer than 4000
    characters to be fully returned.  [ticket:2071]
    (also in 0.6.7)

- firebird
  - The "implicit_returning" flag on create_engine() is
    honored if set to False.  [ticket:2083] (also in 0.6.7)

- informix

  - Added RESERVED_WORDS informix dialect. [ticket:2092]
    (also in 0.6.7)

- ext
  - The horizontal_shard ShardedSession class accepts the common
    Session argument "query_cls" as a constructor argument,
    to enable further subclassing of ShardedQuery.
    [ticket:2090] (also in 0.6.7)

- examples
  - Updated the association, association proxy examples
    to use declarative, added a new example
    dict_of_sets_with_default.py, a "pushing the envelope"
    example of association proxy.

  - The Beaker caching example allows a "query_cls" argument
    to the query_callable() function.  [ticket:2090]
    (also in 0.6.7)

0.7.0b2
========
- orm
  - Fixed bug whereby Session.merge() would call the
    load() event with one too few arguments.
    [ticket:2053]

  - Added logic which prevents the generation of
    events from a MapperExtension or SessionExtension
    from generating do-nothing events for all the methods
    not overridden. [ticket:2052]

- declarative
  - Fixed regression whereby composite() with
    Column objects placed inline would fail
    to initialize.  The Column objects can now
    be inline with the composite() or external
    and pulled in via name or object ref.
    [ticket:2058]

  - Fix error message referencing old @classproperty
    name to reference @declared_attr [ticket:2061]
    (also in 0.6.7)

  - the dictionary at the end of the __table_args__
    tuple is now optional.  [ticket:1468]

- sql
  - Renamed the EngineEvents event class to
    ConnectionEvents.  As these classes are never
    accessed directly by end-user code, this strictly
    is a documentation change for end users.  Also
    simplified how events get linked to engines
    and connections internally. [ticket:2059]

  - The Sequence() construct, when passed a MetaData()
    object via its 'metadata' argument, will be
    included in CREATE/DROP statements within
    metadata.create_all() and metadata.drop_all(),
    including "checkfirst" logic.  [ticket:2055]

  - The Column.references() method now returns True
    if it has a foreign key referencing the
    given column exactly, not just it's parent
    table.  [ticket:2064]

- postgresql
  - Fixed regression from 0.6 where SMALLINT and
    BIGINT types would both generate SERIAL
    on an integer PK column, instead of
    SMALLINT and BIGSERIAL [ticket:2065]

- ext
  - Association proxy now has correct behavior for
    any(), has(), and contains() when proxying
    a many-to-one scalar attribute to a one-to-many
    collection (i.e. the reverse of the 'typical'
    association proxy use case)  [ticket:2054]

- examples
  - Beaker example now takes into account 'limit'
    and 'offset', bind params within embedded
    FROM clauses (like when you use union() or
    from_self()) when generating a cache key.

0.7.0b1
=======
- Detailed descriptions of each change below are
  described at:
  http://www.sqlalchemy.org/trac/wiki/07Migration

- general
  - New event system, supercedes all extensions, listeners,
    etc.  [ticket:1902]

  - Logging enhancements
    [ticket:1926]

  - Setup no longer installs a Nose plugin
    [ticket:1949]

  - The "sqlalchemy.exceptions" alias in sys.modules
    has been removed.   Base SQLA exceptions are
    available via "from sqlalchemy import exc".
    The "exceptions" alias for "exc" remains in
    "sqlalchemy" for now, it's just not patched into
    sys.modules.

- orm
  - More succinct form of query.join(target, onclause)
    [ticket:1923]

  - Hybrid Attributes, implements/supercedes synonym()
    [ticket:1903]

  - Rewrite of composites [ticket:2008]

  - Mutation Event Extension, supercedes "mutable=True"

  - PickleType and ARRAY mutability turned off by default
     [ticket:1980]

  - Simplified polymorphic_on assignment
    [ticket:1895]

  - Flushing of Orphans that have no parent is allowed
    [ticket:1912]

  - Adjusted flush accounting step to occur before
    the commit in the case of autocommit=True.  This allows
    autocommit=True to work appropriately with
    expire_on_commit=True, and also allows post-flush session
    hooks to operate in the same transactional context
    as when autocommit=False.  [ticket:2041]

  - Warnings generated when collection members, scalar referents
    not part of the flush
    [ticket:1973]

  - Non-`Table`-derived constructs can be mapped
    [ticket:1876]

  - Tuple label names in Query Improved
    [ticket:1942]

  - Mapped column attributes reference the most specific
    column first
    [ticket:1892]

  - Mapping to joins with two or more same-named columns
    requires explicit declaration
    [ticket:1896]

  - Mapper requires that polymorphic_on column be present
    in the mapped selectable
    [ticket:1875]

  - compile_mappers() renamed configure_mappers(), simplified
    configuration internals
    [ticket:1966]

  - the aliased() function, if passed a SQL FromClause element
    (i.e. not a mapped class), will return element.alias()
    instead of raising an error on AliasedClass.  [ticket:2018]

  - Session.merge() will check the version id of the incoming
    state against that of the database, assuming the mapping
    uses version ids and incoming state has a version_id
    assigned, and raise StaleDataError if they don't
    match.  [ticket:2027]

  - Session.connection(), Session.execute() accept 'bind',
    to allow execute/connection operations to participate
    in the open transaction of an engine explicitly.
    [ticket:1996]

  - Query.join(), Query.outerjoin(), eagerload(),
    eagerload_all(), others no longer allow lists
    of attributes as arguments (i.e. option([x, y, z])
    form, deprecated since 0.5)

  - ScopedSession.mapper is removed (deprecated since 0.5).

  - Horizontal shard query places 'shard_id' in
    context.attributes where it's accessible by the
    "load()" event. [ticket:2031]

  - A single contains_eager() call across
    multiple entities will indicate all collections
    along that path should load, instead of requiring
    distinct contains_eager() calls for each endpoint
    (which was never correctly documented).
    [ticket:2032]

  - The "name" field used in orm.aliased() now renders
    in the resulting SQL statement.

  - Session weak_instance_dict=False is deprecated.
    [ticket:1473]

  - An exception is raised in the unusual case that an
    append or similar event on a collection occurs after
    the parent object has been dereferenced, which
    prevents the parent from being marked as "dirty"
    in the session.  Was a warning in 0.6.6.
    [ticket:2046]

  - Query.distinct() now accepts column expressions
    as *args, interpreted by the Postgresql dialect
    as DISTINCT ON (<expr>). [ticket:1069]

  - Additional tuning to "many-to-one" relationship
    loads during a flush().   A change in version 0.6.6
    ([ticket:2002]) required that more "unnecessary" m2o
    loads during a flush could occur.   Extra loading modes have
    been added so that the SQL emitted in this
    specific use case is trimmed back, while still
    retrieving the information the flush needs in order
    to not miss anything.  [ticket:2049]

  - the value of "passive" as passed to
    attributes.get_history() should be one of the
    constants defined in the attributes package.  Sending
    True or False is deprecated.

  - Added a `name` argument to `Query.subquery()`, to allow
    a fixed name to be assigned to the alias object.
    [ticket:2030] (also in 0.6.7)

  - A warning is emitted when a joined-table inheriting mapper
    has no primary keys on the locally mapped table
    (but has pks on the superclass table).  [ticket:2019]
    (also in 0.6.7)

  - Fixed bug where "middle" class in a polymorphic hierarchy
    would have no 'polymorphic_on' column if it didn't also
    specify a 'polymorphic_identity', leading to strange
    errors upon refresh, wrong class loaded when querying
    from that target. Also emits the correct WHERE criterion
    when using single table inheritance. [ticket:2038]
    (also in 0.6.7)

 - Fixed bug where a column with a SQL or server side default
   that was excluded from a mapping with include_properties
   or exclude_properties would result in UnmappedColumnError.
   [ticket:1995] (also in 0.6.7)

  - A warning is emitted in the unusual case that an
    append or similar event on a collection occurs after
    the parent object has been dereferenced, which
    prevents the parent from being marked as "dirty"
    in the session.  This will be an exception in 0.7.
    [ticket:2046] (also in 0.6.7)

- declarative
  - Added an explicit check for the case that the name
    'metadata' is used for a column attribute on a
    declarative class. [ticket:2050] (also in 0.6.7)

- sql
  - Added over() function, method to FunctionElement
    classes, produces the _Over() construct which
    in turn generates "window functions", i.e.
    "<window function> OVER (PARTITION BY <partition by>,
    ORDER BY <order by>)".
    [ticket:1844]

  - LIMIT/OFFSET clauses now use bind parameters
    [ticket:805]

  - select.distinct() now accepts column expressions
    as *args, interpreted by the Postgresql dialect
    as DISTINCT ON (<expr>).  Note this was already
    available via passing a list to the `distinct`
    keyword argument to select(). [ticket:1069]

  - select.prefix_with() accepts multiple expressions
    (i.e. *expr), 'prefix' keyword argument to select()
    accepts a list or tuple.

  - Passing a string to the `distinct` keyword argument
    of `select()` for the purpose of emitting special
    MySQL keywords (DISTINCTROW etc.) is deprecated -
    use `prefix_with()` for this.

  - TypeDecorator works with primary key columns
    [ticket:2005] [ticket:2006]

  - DDL() constructs now escape percent signs
    [ticket:1897]

  - Table.c / MetaData.tables refined a bit, don't allow direct
    mutation  [ticket:1893] [ticket:1917]

  - Callables passed to `bindparam()` don't get evaluated
    [ticket:1950]

  - types.type_map is now private, types._type_map
    [ticket:1870]

  - Non-public Pool methods underscored
    [ticket:1982]

  - Added NULLS FIRST and NULLS LAST support. It's implemented
    as an extension to the asc() and desc() operators, called
    nullsfirst() and nullslast().  [ticket:723]

  - The Index() construct can be created inline with a Table
    definition, using strings as column names, as an alternative
    to the creation of the index outside of the Table.

  - execution_options() on Connection accepts
    "isolation_level" argument, sets transaction isolation
    level for that connection only until returned to the
    connection pool, for thsoe backends which support it
    (SQLite, Postgresql) [ticket:2001]

  - A TypeDecorator of Integer can be used with a primary key
    column, and the "autoincrement" feature of various dialects
    as well as the "sqlite_autoincrement" flag will honor
    the underlying database type as being Integer-based.
    [ticket:2005]

  - Established consistency when server_default is present
    on an Integer PK column.  SQLA doesn't pre-fetch these,
    nor do they come back in cursor.lastrowid (DBAPI).
    Ensured all backends consistently return None
    in result.inserted_primary_key for these. Regarding
    reflection for this case, reflection of an int PK col
    with a server_default sets the "autoincrement" flag to False,
    except in the case of a PG SERIAL col where we detected a
    sequence default. [ticket:2020] [ticket:2021]

  - Result-row processors are applied to pre-executed SQL
    defaults, as well as cursor.lastrowid, when determining
    the contents of result.inserted_primary_key.
    [ticket:2006]

  - Bind parameters present in the "columns clause" of a select
    are now auto-labeled like other "anonymous" clauses,
    which among other things allows their "type" to be meaningful
    when the row is fetched, as in result row processors.

  - TypeDecorator is present in the "sqlalchemy" import space.

  - Non-DBAPI errors which occur in the scope of an `execute()`
    call are now wrapped in sqlalchemy.exc.StatementError,
    and the text of the SQL statement and repr() of params
    is included.  This makes it easier to identify statement
    executions which fail before the DBAPI becomes
    involved.  [ticket:2015]

  - The concept of associating a ".bind" directly with a
    ClauseElement has been explicitly moved to Executable,
    i.e. the mixin that describes ClauseElements which represent
    engine-executable constructs.  This change is an improvement
    to internal organization and is unlikely to affect any
    real-world usage.  [ticket:2048]

  - Column.copy(), as used in table.tometadata(), copies the
    'doc' attribute.  [ticket:2028] (also in 0.6.7)

  - Added some defs to the resultproxy.c extension so that
    the extension compiles and runs on Python 2.4.
    [ticket:2023] (also in 0.6.7)

  - The compiler extension now supports overriding the default
    compilation of expression._BindParamClause including that
    the auto-generated binds within the VALUES/SET clause
    of an insert()/update() statement will also use the new
    compilation rules. [ticket:2042] (also in 0.6.7)

-sqlite
  - SQLite dialect now uses `NullPool` for file-based databases
    [ticket:1921]

  - The path given as the location of a sqlite database is now
    normalized via os.path.abspath(), so that directory changes
    within the process don't affect the ultimate location
    of a relative file path.  [ticket:2036]

- postgresql
  - When explicit sequence execution derives the name
    of the auto-generated sequence of a SERIAL column,
    which currently only occurs if implicit_returning=False,
    now accommodates if the table + column name is greater
    than 63 characters using the same logic Postgresql uses.
    [ticket:1083] (also in 0.6.7)

  - Added an additional libpq message to the list of "disconnect"
    exceptions, "could not receive data from server"
    [ticket:2044] (also in 0.6.7)

- mssql
  - the String/Unicode types, and their counterparts VARCHAR/
    NVARCHAR, emit "max" as the length when no length is
    specified, so that the default length, normally '1'
    as per SQL server documentation, is instead
    'unbounded'.  This also occurs for the VARBINARY type.
    [ticket:1833].

    This behavior makes these types more closely compatible
    with Postgresql's VARCHAR type which is similarly unbounded
    when no length is specified.

- mysql
  - New DBAPI support for pymysql, a pure Python port
    of MySQL-python.  [ticket:1991]

  - oursql dialect accepts the same "ssl" arguments in
    create_engine() as that of MySQLdb.  [ticket:2047]
    (also in 0.6.7)

- firebird
  - Some adjustments so that Interbase is supported as well.
    FB/Interbase version idents are parsed into a structure
    such as (8, 1, 1, 'interbase') or (2, 1, 588, 'firebird')
    so they can be distinguished. [ticket:1885]

- drizzle
  - New dialect for Drizzle, a MySQL variant.  Uses MySQL-python
    for the DBAPI.  [ticket:2003]

0.6.7 - 0.6.xx
==============

Changes which apply to 0.6.7 and subsequent versions of 0.6
are listed in the CHANGES file within the 0.6 branch.  All
those changes which are also in the 0.7 series (which is typically
all of them) are listed inline within the 0.7 changes above,
those which apply to an 0.6 release are noted.

0.6.6
=====
- orm
  - Fixed bug whereby a non-"mutable" attribute modified event
    which occurred on an object that was clean except for
    preceding mutable attribute changes would fail to strongly
    reference itself in the identity map. This would cause the
    object to be garbage collected, losing track of any changes
    that weren't previously saved in the "mutable changes"
    dictionary.

  - Fixed bug whereby "passive_deletes='all'" wasn't passing
    the correct symbols to lazy loaders during flush, thereby
    causing an unwarranted load.  [ticket:2013]

  - Fixed bug which prevented composite mapped
    attributes from being used on a mapped select statement.
    [ticket:1997]. Note the workings of composite are slated to
    change significantly in 0.7.

  - active_history flag also added to composite().
    The flag has no effect in 0.6, but is instead
    a placeholder flag for forwards compatibility,
    as it applies in 0.7 for composites.
    [ticket:1976]

  - Fixed uow bug whereby expired objects passed to
    Session.delete() would not have unloaded references
    or collections taken into account when deleting
    objects, despite passive_deletes remaining at
    its default of False.  [ticket:2002]

  - A warning is emitted when version_id_col is specified
    on an inheriting mapper when the inherited mapper
    already has one, if those column expressions are not
    the same.  [ticket:1987]

  - "innerjoin" flag doesn't take effect along the chain
    of joinedload() joins if a previous join in that chain
    is an outer join, thus allowing primary rows without
    a referenced child row to be correctly returned
    in results.  [ticket:1954]

  - Fixed bug regarding "subqueryload" strategy whereby
    strategy would fail if the entity was an aliased()
    construct.  [ticket:1964]

  - Fixed bug regarding "subqueryload" strategy whereby
    the join would fail if using a multi-level load
    of the form from A->joined-subclass->C [ticket:2014]

  - Fixed indexing of Query objects by -1. It was erroneously
    transformed to the empty slice -1:0 that resulted in
    IndexError. [ticket:1968]

  - The mapper argument "primary_key" can be passed as a
    single column as well as a list or tuple.  [ticket:1971]
    The documentation examples that illustrated it as a
    scalar value have been changed to lists.

  - Added active_history flag to relationship()
    and column_property(), forces attribute events to
    always load the "old" value, so that it's available to
    attributes.get_history(). [ticket:1961]

  - Query.get() will raise if the number of params
    in a composite key is too large, as well as too
    small. [ticket:1977]

  - Backport of "optimized get" fix from 0.7,
    improves the generation of joined-inheritance
    "load expired row" behavior.  [ticket:1992]

  - A little more verbiage to the "primaryjoin" error,
    in an unusual condition that the join condition
    "works" for viewonly but doesn't work for non-viewonly,
    and foreign_keys wasn't used - adds "foreign_keys" to
    the suggestion.  Also add "foreign_keys" to the
    suggestion for the generic "direction" error.

- sql
  - Fixed operator precedence rules for multiple
    chains of a single non-associative operator.
    I.e. "x - (y - z)" will compile as "x - (y - z)"
    and not "x - y - z".  Also works with labels,
    i.e. "x - (y - z).label('foo')"
    [ticket:1984]

  - The 'info' attribute of Column is copied during
    Column.copy(), i.e. as occurs when using columns
    in declarative mixins.  [ticket:1967]

  - Added a bind processor for booleans which coerces
    to int, for DBAPIs such as pymssql that naively call
    str() on values.

  - CheckConstraint will copy its 'initially', 'deferrable',
    and '_create_rule' attributes within a copy()/tometadata()
    [ticket:2000]

- engine
  - The "unicode warning" against non-unicode bind data
    is now raised only when the
    Unicode type is used explictly; not when
    convert_unicode=True is used on the engine
    or String type.

  - Fixed memory leak in C version of Decimal result
    processor.  [ticket:1978]

  - Implemented sequence check capability for the C
    version of RowProxy, as well as 2.7 style
    "collections.Sequence" registration for RowProxy.
    [ticket:1871]

  - Threadlocal engine methods rollback(), commit(),
    prepare() won't raise if no transaction is in progress;
    this was a regression introduced in 0.6.  [ticket:1998]

  - Threadlocal engine returns itself upon begin(),
    begin_nested(); engine then implements contextmanager
    methods to allow the "with" statement. [ticket:2004]

- postgresql
  - Single element tuple expressions inside an IN clause
    parenthesize correctly, also from [ticket:1984]

  - Ensured every numeric, float, int code, scalar + array,
    are recognized by psycopg2 and pg8000's "numeric"
    base type. [ticket:1955]

  - Added as_uuid=True flag to the UUID type, will receive
    and return values as Python UUID() objects rather than
    strings.  Currently, the UUID type is only known to
    work with psycopg2.  [ticket:1956]

  - Fixed bug whereby KeyError would occur with non-ENUM
    supported PG versions after a pool dispose+recreate
    would occur, [ticket:1989]

- mysql
  - Fixed error handling for Jython + zxjdbc, such that
    has_table() property works again.  Regression from
    0.6.3 (we don't have a Jython buildbot, sorry)
    [ticket:1960]

- sqlite
  - The REFERENCES clause in a CREATE TABLE that includes
    a remote schema to another table with the same schema
    name now renders the remote name without
    the schema clause, as required by SQLite.  [ticket:1851]

  - On the same theme, the REFERENCES clause in a CREATE TABLE
    that includes a remote schema to a *different* schema
    than that of the parent table doesn't render at all,
    as cross-schema references do not appear to be supported.

- mssql
   - The rewrite of index reflection in [ticket:1770] was
     unfortunately not tested correctly, and returned incorrect
     results.   This regression is now fixed.

- oracle
  - The cx_oracle "decimal detection" logic, which takes place
    for for result set columns with ambiguous numeric characteristics,
    now uses the decimal point character determined by the locale/
    NLS_LANG setting, using an on-first-connect detection of
    this character.  cx_oracle 5.0.3 or greater is also required
    when using a non-period-decimal-point NLS_LANG setting.
    [ticket:1953].

- firebird
  - Firebird numeric type now checks for Decimal explicitly,
    lets float() pass right through, thereby allowing
    special values such as float('inf'). [ticket:2012]

- declarative
  - An error is raised if __table_args__ is not in tuple
    or dict format, and is not None.  [ticket:1972]

- sqlsoup
  - Added "map_to()" method to SqlSoup, which is a "master"
    method which accepts explicit arguments for each aspect of
    the selectable and mapping, including a base class per
    mapping. [ticket:1975]

  - Mapped selectables used with the map(), with_labels(),
    join() methods no longer put the given argument into the
    internal "cache" dictionary.  Particularly since the
    join() and select() objects are created in the method
    itself this was pretty much a pure memory leaking behavior.

- examples
  - The versioning example now supports detection of changes
    in an associated relationship().

0.6.5
=====
- orm
  - Added a new "lazyload" option "immediateload".
    Issues the usual "lazy" load operation automatically
    as the object is populated.   The use case
    here is when loading objects to be placed in
    an offline cache, or otherwise used after
    the session isn't available, and straight 'select'
    loading, not 'joined' or 'subquery', is desired.
    [ticket:1914]

  - New Query methods: query.label(name), query.as_scalar(),
    return the query's statement as a scalar subquery
    with /without label [ticket:1920];
    query.with_entities(*ent), replaces the SELECT list of
    the query with new entities.
    Roughly equivalent to a generative form of query.values()
    which accepts mapped entities as well as column
    expressions.

  - Fixed recursion bug which could occur when moving
    an object from one reference to another, with
    backrefs involved, where the initiating parent
    was a subclass (with its own mapper) of the
    previous parent.

  - Fixed a regression in 0.6.4 which occurred if you
    passed an empty list to "include_properties" on
    mapper() [ticket:1918]

  - Fixed labeling bug in Query whereby the NamedTuple
    would mis-apply labels if any of the column
    expressions were un-labeled.

  - Patched a case where query.join() would adapt the
    right side to the right side of the left's join
    inappropriately [ticket:1925]

  - Query.select_from() has been beefed up to help
    ensure that a subsequent call to query.join()
    will use the select_from() entity, assuming it's
    a mapped entity and not a plain selectable,
    as the default "left" side, not the first entity
    in the Query object's list of entities.

  - The exception raised by Session when it is used
    subsequent to a subtransaction rollback (which is what
    happens when a flush fails in autocommit=False mode) has
    now been reworded (this is the "inactive due to a
    rollback in a subtransaction" message). In particular,
    if the rollback was due to an exception during flush(),
    the message states this is the case, and reiterates the
    string form of the original exception that occurred
    during flush. If the session is closed due to explicit
    usage of subtransactions (not very common), the message
    just states this is the case.

  - The exception raised by Mapper when repeated requests to
    its initialization are made after initialization already
    failed no longer assumes the "hasattr" case, since
    there's other scenarios in which this message gets
    emitted, and the message also does not compound onto
    itself multiple times - you get the same message for
    each attempt at usage. The misnomer "compiles" is being
    traded out for "initialize".

  - Fixed bug in query.update() where 'evaluate' or 'fetch'
    expiration would fail if the column expression key was
    a class attribute with a different keyname as the
    actual column name.  [ticket:1935]

  - Added an assertion during flush which ensures
    that no NULL-holding identity keys were generated
    on "newly persistent" objects.
    This can occur when user defined code inadvertently
    triggers flushes on not-fully-loaded objects.

  - lazy loads for relationship attributes now use
    the current state, not the "committed" state,
    of foreign and primary key attributes
    when issuing SQL, if a flush is not in process.
    Previously, only the database-committed state would
    be used.  In particular, this would cause a many-to-one
    get()-on-lazyload operation to fail, as autoflush
    is not triggered on these loads when the attributes are
    determined and the "committed" state may not be
    available.  [ticket:1910]

  - A new flag on relationship(), load_on_pending, allows
    the lazy loader to fire off on pending objects without a
    flush taking place, as well as a transient object that's
    been manually "attached" to the session. Note that this
    flag blocks attribute events from taking place when an
    object is loaded, so backrefs aren't available until
    after a flush. The flag is only intended for very
    specific use cases.

  - Another new flag on relationship(), cascade_backrefs,
    disables the "save-update" cascade when the event was
    initiated on the "reverse" side of a bidirectional
    relationship.   This is a cleaner behavior so that
    many-to-ones can be set on a transient object without
    it getting sucked into the child object's session,
    while still allowing the forward collection to
    cascade.   We *might* default this to False in 0.7.

  - Slight improvement to the behavior of
    "passive_updates=False" when placed only on the
    many-to-one side of a relationship; documentation has
    been clarified that passive_updates=False should really
    be on the one-to-many side.

  - Placing passive_deletes=True on a many-to-one emits
    a warning, since you probably intended to put it on
    the one-to-many side.

  - Fixed bug that would prevent "subqueryload" from
    working correctly with single table inheritance
    for a relationship from a subclass - the "where
    type in (x, y, z)" only gets placed on the inside,
    instead of repeatedly.

  - When using from_self() with single table inheritance,
    the "where type in (x, y, z)" is placed on the outside
    of the query only, instead of repeatedly.   May make
    some more adjustments to this.

  - scoped_session emits a warning when configure() is
    called if a Session is already present (checks only the
    current thread) [ticket:1924]

  - reworked the internals of mapper.cascade_iterator() to
    cut down method calls by about 9% in some circumstances.
    [ticket:1932]

- sql
   - Fixed bug in TypeDecorator whereby the dialect-specific
     type was getting pulled in to generate the DDL for a
     given type, which didn't always return the correct result.

   - TypeDecorator can now have a fully constructed type
     specified as its "impl", in addition to a type class.

   - TypeDecorator will now place itself as the resulting
     type for a binary expression where the type coercion
     rules would normally return its impl type - previously,
     a copy of the impl type would be returned which would
     have the TypeDecorator embedded into it as the "dialect"
     impl, this was probably an unintentional way of achieving
     the desired effect.

   - TypeDecorator.load_dialect_impl() returns "self.impl" by
     default, i.e. not the dialect implementation type of
     "self.impl".   This to support compilation correctly.
     Behavior can be user-overridden in exactly the same way
     as before to the same effect.

   - Added type_coerce(expr, type_) expression element.
     Treats the given expression as the given type when evaluating
     expressions and processing result rows, but does not
     affect the generation of SQL, other than an anonymous
     label.

   - Table.tometadata() now copies Index objects associated
     with the Table as well.

   - Table.tometadata() issues a warning if the given Table
     is already present in the target MetaData - the existing
     Table object is returned.

   - An informative error message is raised if a Column
     which has not yet been assigned a name, i.e. as in
     declarative, is used in a context where it is
     exported to the columns collection of an enclosing
     select() construct, or if any construct involving
     that column is compiled before its name is
     assigned.

   - as_scalar(), label() can be called on a selectable
     which contains a Column that is not yet named.
     [ticket:1862]

   - Fixed recursion overflow which could occur when operating
     with two expressions both of type "NullType", but
     not the singleton NULLTYPE instance. [ticket:1907]

- declarative
   - @classproperty (soon/now @declared_attr) takes effect for
     __mapper_args__, __table_args__, __tablename__ on
     a base class that is not a mixin, as well as mixins.
     [ticket:1922]

   - @classproperty 's official name/location for usage
     with declarative is sqlalchemy.ext.declarative.declared_attr.
     Same thing, but moving there since it is more of a
     "marker" that's specific to declararative,
     not just an attribute technique.  [ticket:1915]

   - Fixed bug whereby columns on a mixin wouldn't propagate
     correctly to a single-table, or joined-table,
     inheritance scheme where the attribute name is
     different than that of the column. [ticket:1930],
     [ticket:1931].

   - A mixin can now specify a column that overrides
     a column of the same name associated with a superclass.
     Thanks to Oystein Haaland.

- engine

   - Fixed a regression in 0.6.4 whereby the change that
     allowed cursor errors to be raised consistently broke
     the result.lastrowid accessor.   Test coverage has
     been added for result.lastrowid.   Note that lastrowid
     is only supported by Pysqlite and some MySQL drivers,
     so isn't super-useful in the general case.

   - the logging message emitted by the engine when
     a connection is first used is now "BEGIN (implicit)"
     to emphasize that DBAPI has no explicit begin().

   - added "views=True" option to metadata.reflect(),
     will add the list of available views to those
     being reflected.  [ticket:1936]

   - engine_from_config() now accepts 'debug' for
     'echo', 'echo_pool', 'force' for 'convert_unicode',
     boolean values for 'use_native_unicode'.
     [ticket:1899]

- postgresql
   - Added "as_tuple" flag to ARRAY type, returns results
     as tuples instead of lists to allow hashing.

   - Fixed bug which prevented "domain" built from a
     custom type such as "enum" from being reflected.
     [ticket:1933]

- mysql
   - Fixed bug involving reflection of CURRENT_TIMESTAMP
     default used with ON UPDATE clause, thanks to
     Taavi Burns [ticket:1940]

- oracle
   - The implicit_retunring argument to create_engine()
     is now honored regardless of detected version of
     Oracle.  Previously, the flag would be forced
     to False if server version info was < 10.
     [ticket:1878]

- mssql
   - Fixed reflection bug which did not properly handle
     reflection of unknown types.  [ticket:1946]

   - Fixed bug where aliasing of tables with "schema" would
     fail to compile properly.  [ticket:1943]

   - Rewrote the reflection of indexes to use sys.
     catalogs, so that column names of any configuration
     (spaces, embedded commas, etc.) can be reflected.
     Note that reflection of indexes requires SQL
     Server 2005 or greater.  [ticket:1770]

   - mssql+pymssql dialect now honors the "port" portion
     of the URL instead of discarding it.  [ticket:1952]

- informix
   - *Major* cleanup / modernization of the Informix
     dialect for 0.6, courtesy Florian Apolloner.
     [ticket:1906]

- tests
   - the NoseSQLAlchemyPlugin has been moved to a
     new package "sqlalchemy_nose" which installs
     along with "sqlalchemy".  This so that the "nosetests"
     script works as always but also allows the
     --with-coverage option to turn on coverage before
     SQLAlchemy modules are imported, allowing coverage
     to work correctly.

- misc
   - CircularDependencyError now has .cycles and .edges
     members, which are the set of elements involved in
     one or more cycles, and the set of edges as 2-tuples.
     [ticket:1890]

0.6.4
=====
- orm
  - The name ConcurrentModificationError has been
    changed to StaleDataError, and descriptive
    error messages have been revised to reflect
    exactly what the issue is.   Both names will
    remain available for the forseeable future
    for schemes that may be specifying
    ConcurrentModificationError in an "except:"
    clause.

  - Added a mutex to the identity map which mutexes
    remove operations against iteration methods,
    which now pre-buffer before returning an
    iterable.   This because asyncrhonous gc
    can remove items via the gc thread at any time.
    [ticket:1891]

  - The Session class is now present in sqlalchemy.orm.*.
    We're moving away from the usage of create_session(),
    which has non-standard defaults, for those situations
    where a one-step Session constructor is desired. Most
    users should stick with sessionmaker() for general use,
    however.

  - query.with_parent() now accepts transient objects
    and will use the non-persistent values of their pk/fk
    attributes in order to formulate the criterion.
    Docs are also clarified as to the purpose of with_parent().

  - The include_properties and exclude_properties arguments
    to mapper() now accept Column objects as members in
    addition to strings.  This so that same-named Column
    objects, such as those within a join(), can be
    disambiguated.

  - A warning is now emitted if a mapper is created against a
    join or other single selectable that includes multiple
    columns with the same name in its .c. collection,
    and those columns aren't explictly named as part of
    the same or separate attributes (or excluded).
    In 0.7 this warning will be an exception.   Note that
    this warning is not emitted when the combination occurs
    as a result of inheritance, so that attributes
    still allow being overridden naturally.
    [ticket:1896].  In 0.7 this will be improved further.

  - The primary_key argument to mapper() can now specify
    a series of columns that are only a subset of
    the calculated "primary key" columns of the mapped
    selectable, without an error being raised.  This
    helps for situations where a selectable's effective
    primary key is simpler than the number of columns
    in the selectable that are actually marked as
    "primary_key", such as a join against two
    tables on their primary key columns [ticket:1896].

  - An object that's been deleted now gets a flag
    'deleted', which prohibits the object from
    being re-add()ed to the session, as previously
    the object would live in the identity map
    silently until its attributes were accessed.
    The make_transient() function now resets this
    flag along with the "key" flag.

  - make_transient() can be safely called on an
    already transient instance.

  - a warning is emitted in mapper() if the polymorphic_on
    column is not present either in direct or derived
    form in the mapped selectable or in the
    with_polymorphic selectable, instead of silently
    ignoring it.  Look for this to become an
    exception in 0.7.

  - Another pass through the series of error messages
    emitted when relationship() is configured with
    ambiguous arguments.   The "foreign_keys"
    setting is no longer mentioned, as it is almost
    never needed and it is preferable users set up
    correct ForeignKey metadata, which is now the
    recommendation.  If 'foreign_keys'
    is used and is incorrect, the message suggests
    the attribute is probably unnecessary.  Docs
    for the attribute are beefed up.  This
    because all confused relationship() users on the
    ML appear to be attempting to use foreign_keys
    due to the message, which only confuses them
    further since Table metadata is much clearer.

  - If the "secondary" table has no ForeignKey metadata
    and no foreign_keys is set, even though the
    user is passing screwed up information, it is assumed
    that primary/secondaryjoin expressions should
    consider only and all cols in "secondary" to be
    foreign.  It's not possible with "secondary" for
    the foreign keys to be elsewhere in any case.
    A warning is now emitted instead of an error,
    and the mapping succeeds. [ticket:1877]

  - Moving an o2m object from one collection to
    another, or vice versa changing the referenced
    object by an m2o, where the foreign key is also a
    member of the primary key, will now be more
    carefully checked during flush if the change in
    value of the foreign key on the "many" side is the
    result of a change in the primary key of the "one"
    side, or if the "one" is just a different object.
    In one case, a cascade-capable DB would have
    cascaded the value already and we need to look at
    the "new" PK value to do an UPDATE, in the other we
    need to continue looking at the "old". We now look
    at the "old", assuming passive_updates=True,
    unless we know it was a PK switch that
    triggered the change. [ticket:1856]

  - The value of version_id_col can be changed
    manually, and this will result in an UPDATE
    of the row.  Versioned UPDATEs and DELETEs
    now use the "committed" value of the
    version_id_col in the WHERE clause and
    not the pending changed value. The
    version generator is also bypassed if
    manual changes are present on the attribute.
    [ticket:1857]

  - Repaired the usage of merge() when used with
    concrete inheriting mappers.  Such mappers frequently
    have so-called "concrete" attributes, which are
    subclass attributes that "disable" propagation from
    the parent - these needed to allow a merge()
    operation to pass through without effect.

  - Specifying a non-column based argument
    for column_mapped_collection, including string,
    text() etc., will raise an error message that
    specifically asks for a column element, no longer
    misleads with incorrect information about
    text() or literal().  [ticket:1863]

  - Similarly, for relationship(), foreign_keys,
    remote_side, order_by - all column-based
    expressions are enforced - lists of strings
    are explicitly disallowed since this is a
    very common error

  - Dynamic attributes don't support collection
    population - added an assertion for when
    set_committed_value() is called, as well as
    when joinedload() or subqueryload() options
    are applied to a dynamic attribute, instead
    of failure / silent failure.  [ticket:1864]

  - Fixed bug whereby generating a Query derived
    from one which had the same column repeated
    with different label names, typically
    in some UNION situations, would fail to
    propagate the inner columns completely to
    the outer query.  [ticket:1852]

  - object_session() raises the proper
    UnmappedInstanceError when presented with an
    unmapped instance.  [ticket:1881]

  - Applied further memoizations to calculated Mapper
    properties, with significant (~90%) runtime mapper.py
    call count reduction in heavily polymorphic mapping
    configurations.

  - mapper _get_col_to_prop private method used
    by the versioning example is deprecated;
    now use mapper.get_property_by_column() which
    will remain the public method for this.

  - the versioning example works correctly now
    if versioning on a col that was formerly
    NULL.

- sql
  - Calling execute() on an alias() construct is pending
    deprecation for 0.7, as it is not itself an
    "executable" construct. It currently "proxies" its
    inner element and is conditionally "executable" but
    this is not the kind of ambiguity we like these days.

  - The execute() and scalar() methods of ClauseElement
    are now moved appropriately to the Executable
    subclass. ClauseElement.execute()/ scalar() are still
    present and are pending deprecation in 0.7, but note
    these would always raise an error anyway if you were
    not an Executable (unless you were an alias(), see
    previous note).

  - Added basic math expression coercion for
    Numeric->Integer,
    so that resulting type is Numeric regardless
    of the direction of the expression.

  - Changed the scheme used to generate truncated
    "auto" index names when using the "index=True"
    flag on Column.   The truncation only takes
    place with the auto-generated name, not one
    that is user-defined (an error would be
    raised instead), and the truncation scheme
    itself is now based on a fragment of an md5
    hash of the identifier name, so that multiple
    indexes on columns with similar names still
    have unique names.  [ticket:1855]

  - The generated index name also is based on
    a "max index name length" attribute which is
    separate from the "max identifier length" -
    this to appease MySQL who has a max length
    of 64 for index names, separate from their
    overall max length of 255.  [ticket:1412]

  - the text() construct, if placed in a column
    oriented situation, will at least return NULLTYPE
    for its type instead of None, allowing it to
    be used a little more freely for ad-hoc column
    expressions than before.   literal_column()
    is still the better choice, however.

  - Added full description of parent table/column,
    target table/column in error message raised when
    ForeignKey can't resolve target.

  - Fixed bug whereby replacing composite foreign key
    columns in a reflected table would cause an attempt
    to remove the reflected constraint from the table
    a second time, raising a KeyError.  [ticket:1865]

  - the _Label construct, i.e. the one that is produced
    whenever you say somecol.label(), now counts itself
    in its "proxy_set" unioned with that of it's
    contained column's proxy set, instead of
    directly returning that of the contained column.
    This allows column correspondence
    operations which depend on the identity of the
    _Labels themselves to return the correct result
    - fixes ORM bug [ticket:1852].

- engine

  - Calling fetchone() or similar on a result that
    has already been exhausted, has been closed,
    or is not a result-returning result now
    raises ResourceClosedError, a subclass of
    InvalidRequestError, in all cases, regardless
    of backend.  Previously, some DBAPIs would
    raise ProgrammingError (i.e. pysqlite), others
    would return None leading to downstream breakages
    (i.e. MySQL-python).

  - Fixed bug in Connection whereby if a "disconnect"
    event occurred in the "initialize" phase of the
    first connection pool connect, an AttributeError
    would be raised when the Connection would attempt
    to invalidate the DBAPI connection.  [ticket:1894]

  - Connection, ResultProxy, as well as Session use
    ResourceClosedError for all "this
    connection/transaction/result is closed" types of
    errors.

  - Connection.invalidate() can be called more than
    once and subsequent calls do nothing.

- declarative
  - if @classproperty is used with a regular class-bound
    mapper property attribute, it will be called to get the
    actual attribute value during initialization. Currently,
    there's no advantage to using @classproperty on a column
    or relationship attribute of a declarative class that
    isn't a mixin - evaluation is at the same time as if
    @classproperty weren't used. But here we at least allow
    it to function as expected.

  - Fixed bug where "Can't add additional column" message
    would display the wrong name.

- postgresql
  - Fixed the psycopg2 dialect to use its
    set_isolation_level() method instead of relying
    upon the base "SET SESSION ISOLATION" command,
    as psycopg2 resets the isolation level on each new
    transaction otherwise.

- mssql
  - Fixed "default schema" query to work with
    pymssql backend.

- firebird
  - Fixed bug whereby a column default would fail to
    reflect if the "default" keyword were lower case.

- oracle
  - Added ROWID type to the Oracle dialect, for those
    cases where an explicit CAST might be needed.
    [ticket:1879]

  - Oracle reflection of indexes has been tuned so
    that indexes which include some or all primary
    key columns, but not the same set of columns
    as that of the primary key, are reflected.
    Indexes which contain the identical columns
    as that of the primary key are skipped within
    reflection, as the index in that case is assumed
    to be the auto-generated primary key index.
    Previously, any index with PK columns present
    would be skipped.  Thanks to Kent Bower
    for the patch.  [ticket:1867]

  - Oracle now reflects the names of primary key
    constraints - also thanks to Kent Bower.
    [ticket:1868]

- informix
  - Applied patches from [ticket:1904] to get
    basic Informix functionality up again.  We
    rely upon end-user testing to ensure that
    Informix is working to some degree.

- documentation
  - The docs have been reorganized such that the "API
    Reference" section is gone - all the docstrings from
    there which were public API are moved into the
    context of the main doc section that talks about it.
    Main docs divided into "SQLAlchemy Core" and
    "SQLAlchemy ORM" sections, mapper/relationship docs
    have been broken out. Lots of sections rewritten
    and/or reorganized.

- examples
  - The beaker_caching example has been reorgnized
    such that the Session, cache manager,
    declarative_base are part of environment, and
    custom cache code is portable and now within
    "caching_query.py".  This allows the example to
    be easier to "drop in" to existing projects.

  - the history_meta versioning recipe sets "unique=False"
    when copying columns, so that the versioning
    table handles multiple rows with repeating values.
    [ticket:1887]

0.6.3
=====
- orm
  - Removed errant many-to-many load in unitofwork
    which triggered unnecessarily on expired/unloaded
    collections. This load now takes place only if
    passive_updates is False and the parent primary
    key has changed, or if passive_deletes is False
    and a delete of the parent has occurred.
    [ticket:1845]

  - Column-entities (i.e. query(Foo.id)) copy their
    state more fully when queries are derived from
    themselves + a selectable (i.e. from_self(),
    union(), etc.), so that join() and such have the
    correct state to work from.  [ticket:1853]

  - Fixed bug where Query.join() would fail if
    querying a non-ORM column then joining without
    an on clause when a FROM clause is already
    present, now raises a checked exception the
    same way it does when the clause is not
    present.  [ticket:1853]

  - Improved the check for an "unmapped class",
    including the case where the superclass is mapped
    but the subclass is not.  Any attempts to access
    cls._sa_class_manager.mapper now raise
    UnmappedClassError().  [ticket:1142]

  - Added "column_descriptions" accessor to Query,
    returns a list of dictionaries containing
    naming/typing information about the entities
    the Query will return.  Can be helpful for
    building GUIs on top of ORM queries.

- mysql

  - The _extract_error_code() method now works
    correctly with each MySQL dialect (
    MySQL-python, OurSQL, MySQL-Connector-Python,
    PyODBC).  Previously,
    the reconnect logic would fail for OperationalError
    conditions, however since MySQLdb and OurSQL
    have their own reconnect feature, there was no
    symptom for these drivers here unless one
    watched the logs.  [ticket:1848]

- oracle
  - More tweaks to cx_oracle Decimal handling.
    "Ambiguous" numerics with no decimal place
    are coerced to int at the connection handler
    level.  The advantage here is that ints
    come back as ints without SQLA type
    objects being involved and without needless
    conversion to Decimal first.

    Unfortunately, some exotic subquery cases
    can even see different types between
    individual result rows, so the Numeric
    handler, when instructed to return Decimal,
    can't take full advantage of "native decimal"
    mode and must run isinstance() on every value
    to check if its Decimal already. Reopen of
    [ticket:1840]

0.6.2
=====
- orm
  - Query.join() will check for a call of the
    form query.join(target, clause_expression),
    i.e. missing the tuple, and raise an informative
    error message that this is the wrong calling form.

  - Fixed bug regarding flushes on self-referential
    bi-directional many-to-many relationships, where
    two objects made to mutually reference each other
    in one flush would fail to insert a row for both
    sides.  Regression from 0.5. [ticket:1824]

  - the post_update feature of relationship() has been
    reworked architecturally to integrate more closely
    with the new 0.6 unit of work.  The motivation
    for the change is so that multiple "post update"
    calls, each affecting different foreign key
    columns of the same row, are executed in a single
    UPDATE statement, rather than one UPDATE
    statement per column per row.   Multiple row
    updates are also batched into executemany()s as
    possible, while maintaining consistent row ordering.

  - Query.statement, Query.subquery(), etc. now transfer
    the values of bind parameters, i.e. those specified
    by query.params(), into the resulting SQL expression.
    Previously the values would not be transferred
    and bind parameters would come out as None.

  - Subquery-eager-loading now works with Query objects
    which include params(), as well as get() Queries.

  - Can now call make_transient() on an instance that
    is referenced by parent objects via many-to-one,
    without the parent's foreign key value getting
    temporarily set to None - this was a function
    of the "detect primary key switch" flush handler.
    It now ignores objects that are no longer
    in the "persistent" state, and the parent's
    foreign key identifier is left unaffected.

  - query.order_by() now accepts False, which cancels
    any existing order_by() state on the Query, allowing
    subsequent generative methods to be called which do
    not support ORDER BY.  This is not the same as the
    already existing feature of passing None, which
    suppresses any existing order_by() settings, including
    those configured on the mapper.  False will make it
    as though order_by() was never called, while
    None is an active setting.

  - An instance which is moved to "transient", has
    an incomplete or missing set of primary key
    attributes, and contains expired attributes, will
    raise an InvalidRequestError if an expired attribute
    is accessed, instead of getting a recursion overflow.

  - The make_transient() function is now in the generated
    documentation.

  - make_transient() removes all "loader" callables from
    the state being made transient, removing any
    "expired" state - all unloaded attributes reset back
    to undefined, None/empty on access.

- sql
  - The warning emitted by the Unicode and String types
    with convert_unicode=True no longer embeds the actual
    value passed.   This so that the Python warning
    registry does not continue to grow in size, the warning
    is emitted once as per the warning filter settings,
    and large string values don't pollute the output.
    [ticket:1822]

  - Fixed bug that would prevent overridden clause
    compilation from working for "annotated" expression
    elements, which are often generated by the ORM.

  - The argument to "ESCAPE" of a LIKE operator or similar
    is passed through render_literal_value(), which may
    implement escaping of backslashes.  [ticket:1400]

  - Fixed bug in Enum type which blew away native_enum
    flag when used with TypeDecorators or other adaption
    scenarios.

  - Inspector hits bind.connect() when invoked to ensure
    initialize has been called.  the internal name ".conn"
    is changed to ".bind", since that's what it is.

  - Modified the internals of "column annotation" such that
    a custom Column subclass can safely override
    _constructor to return Column, for the purposes of
    making "configurational" column classes that aren't
    involved in proxying, etc.

  - Column.copy() takes along the "unique" attribute
    among others, fixes [ticket:1829] regarding declarative
    mixins

- postgresql
  - render_literal_value() is overridden which escapes
    backslashes, currently applies to the ESCAPE clause
    of LIKE and similar expressions.
    Ultimately this will have to detect the value of
    "standard_conforming_strings" for full behavior.
    [ticket:1400]

  - Won't generate "CREATE TYPE" / "DROP TYPE" if
    using types.Enum on a PG version prior to 8.3 -
    the supports_native_enum flag is fully
    honored.  [ticket:1836]

- mysql
  - MySQL dialect doesn't emit CAST() for MySQL version
    detected < 4.0.2.  This allows the unicode
    check on connect to proceed. [ticket:1826]

  - MySQL dialect now detects NO_BACKSLASH_ESCAPES sql
    mode, in addition to ANSI_QUOTES.

  - render_literal_value() is overridden which escapes
    backslashes, currently applies to the ESCAPE clause
    of LIKE and similar expressions.   This behavior
    is derived from detecting the value of
    NO_BACKSLASH_ESCAPES.  [ticket:1400]

- oracle:
  - Fixed ora-8 compatibility flags such that they
    don't cache a stale value from before the first
    database connection actually occurs. [ticket:1819]

  - Oracle's "native decimal" metadata begins to return
    ambiguous typing information about numerics
    when columns are embedded in subqueries as well
    as when ROWNUM is consulted with subqueries, as we
    do for limit/offset.  We've added these ambiguous
    conditions to the cx_oracle "convert to Decimal()"
    handler, so that we receive numerics as Decimal
    in more cases instead of as floats.  These are
    then converted, if requested, into Integer
    or Float, or otherwise kept as the lossless
    Decimal [ticket:1840].

- mssql
  - If server_version_info is outside the usual
    range of (8, ), (9, ), (10, ), a warning is emitted
    which suggests checking that the FreeTDS version
    configuration is using 7.0 or 8.0, not 4.2.
    [ticket:1825]

- firebird
  - Fixed incorrect signature in do_execute(), error
    introduced in 0.6.1. [ticket:1823]

  - Firebird dialect adds CHAR, VARCHAR types which
    accept a "charset" flag, to support Firebird
    "CHARACTER SET" clause.  [ticket:1813]

- declarative
   - Added support for @classproperty to provide
     any kind of schema/mapping construct from a
     declarative mixin, including columns with foreign
     keys, relationships, column_property, deferred.
     This solves all such issues on declarative mixins.
     An error is raised if any MapperProperty subclass
     is specified on a mixin without using @classproperty.
     [ticket:1751] [ticket:1796] [ticket:1805]

   - a mixin class can now define a column that matches
     one which is present on a __table__ defined on a
     subclass.  It cannot, however, define one that is
     not present in the __table__, and the error message
     here now works.  [ticket:1821]

- compiler extension
  - The 'default' compiler is automatically copied over
    when overriding the compilation of a built in
    clause construct, so no KeyError is raised if the
    user-defined compiler is specific to certain
    backends and compilation for a different backend
    is invoked. [ticket:1838]

- documentation
  - Added documentation for the Inspector. [ticket:1820]

  - Fixed @memoized_property and @memoized_instancemethod
    decorators so that Sphinx documentation picks up
    these attributes and methods, such as
    ResultProxy.inserted_primary_key. [ticket:1830]


0.6.1
=====
- orm
  - Fixed regression introduced in 0.6.0 involving improper
    history accounting on mutable attributes.  [ticket:1782]

  - Fixed regression introduced in 0.6.0 unit of work refactor
    that broke updates for bi-directional relationship()
    with post_update=True. [ticket:1807]

  - session.merge() will not expire attributes on the returned
    instance if that instance is "pending".  [ticket:1789]

  - fixed __setstate__ method of CollectionAdapter to not
    fail during deserialize where parent InstanceState not
    yet unserialized.  [ticket:1802]

  - Added internal warning in case an instance without a
    full PK happened to be expired and then was asked
    to refresh. [ticket:1797]

  - Added more aggressive caching to the mapper's usage of
    UPDATE, INSERT, and DELETE expressions.  Assuming the
    statement has no per-object SQL expressions attached,
    the expression objects are cached by the mapper after
    the first create, and their compiled form is stored
    persistently in a cache dictionary for the duration of
    the related Engine.  The cache is an LRUCache for the
    rare case that a mapper receives an extremely
    high number of different column patterns as UPDATEs.

- sql
  - expr.in_() now accepts a text() construct as the argument.
    Grouping parenthesis are added automatically, i.e. usage
    is like `col.in_(text("select id from table"))`.
    [ticket:1793]

  - Columns of _Binary type (i.e. LargeBinary, BLOB, etc.)
    will coerce a "basestring" on the right side into a
    _Binary as well so that required DBAPI processing
    takes place.

  - Added table.add_is_dependent_on(othertable), allows manual
    placement of dependency rules between two Table objects
    for use within create_all(), drop_all(), sorted_tables.
    [ticket:1801]

  - Fixed bug that prevented implicit RETURNING from functioning
    properly with composite primary key that contained zeroes.
    [ticket:1778]

  - Fixed errant space character when generating ADD CONSTRAINT
    for a named UNIQUE constraint.

  - Fixed "table" argument on constructor of ForeginKeyConstraint
    [ticket:1571]

  - Fixed bug in connection pool cursor wrapper whereby if a
    cursor threw an exception on close(), the logging of the
    message would fail.  [ticket:1786]

  - the _make_proxy() method of ColumnClause and Column now use
    self.__class__ to determine the class of object to be returned
    instead of hardcoding to ColumnClause/Column, making it slightly
    easier to produce specific subclasses of these which work in
    alias/subquery situations.

  - func.XXX() doesn't inadvertently resolve to non-Function
    classes (e.g. fixes func.text()).  [ticket:1798]

- engines
  - Fixed building the C extensions on Python 2.4. [ticket:1781]

  - Pool classes will reuse the same "pool_logging_name" setting
    after a dispose() occurs.

  - Engine gains an "execution_options" argument and
    update_execution_options() method, which will apply to
    all connections generated by this engine.

- mysql
  - func.sysdate() emits "SYSDATE()", i.e. with the ending
    parenthesis, on MySQL.  [ticket:1794]

- sqlite
  - Fixed concatenation of constraints when "PRIMARY KEY"
    constraint gets moved to column level due to SQLite
    AUTOINCREMENT keyword being rendered.  [ticket:1812]

- oracle
  - Added a check for cx_oracle versions lower than version 5,
    in which case the incompatible "output type handler" won't
    be used.   This will impact decimal accuracy and some
    unicode handling issues.  [ticket:1775]

  - Fixed use_ansi=False mode, which was producing broken
    WHERE clauses in pretty much all cases.  [ticket:1790]

  - Re-established support for Oracle 8 with cx_oracle,
    including that use_ansi is set to False automatically,
    NVARCHAR2 and NCLOB are not rendered for Unicode,
    "native unicode" check doesn't fail, cx_oracle
    "native unicode" mode is disabled, VARCHAR() is emitted
    with bytes count instead of char count. [ticket:1808]

  - oracle_xe 5 doesn't accept a Python unicode object in
    its connect string in normal Python 2.x mode - so we coerce
    to str() directly.  non-ascii characters aren't supported
    in connect strings here since we don't know what encoding
    we could use.  [ticket:1670]

  - FOR UPDATE is emitted in the syntactically correct position
    when limit/offset is used, i.e. the ROWNUM subquery.
    However, Oracle can't really handle FOR UPDATE with ORDER BY
    or with subqueries, so its still not very usable, but at
    least SQLA gets the SQL past the Oracle parser.
    [ticket:1815]

- firebird
  - Added a label to the query used within has_table() and
    has_sequence() to work with older versions of Firebird
    that don't provide labels for result columns. [ticket:1521]

  - Added integer coercion to the "type_conv" attribute when
    passed via query string, so that it is properly interpreted
    by Kinterbasdb. [ticket:1779]

  - Added 'connection shutdown' to the list of exception strings
    which indicate a dropped connection.  [ticket:1646]

- sqlsoup
  - the SqlSoup constructor accepts a `base` argument which specifies
    the base class to use for mapped classes, the default being
    `object`.  [ticket:1783]

0.6.0
=====

- orm
  - Unit of work internals have been rewritten.  Units of work
    with large numbers of objects interdependent objects
    can now be flushed without recursion overflows
    as there is no longer reliance upon recursive calls
    [ticket:1081].  The number of internal structures now stays
    constant for a particular session state, regardless of
    how many relationships are present on mappings.  The flow
    of events now corresponds to a linear list of steps,
    generated by the mappers and relationships based on actual
    work to be done, filtered through a single topological sort
    for correct ordering.  Flush actions are assembled using
    far fewer steps and less memory. [ticket:1742]

  - Along with the UOW rewrite, this also removes an issue
    introduced in 0.6beta3 regarding topological cycle detection
    for units of work with long dependency cycles.  We now use
    an algorithm written by Guido (thanks Guido!).

  - one-to-many relationships now maintain a list of positive
    parent-child associations within the flush, preventing
    previous parents marked as deleted from cascading a
    delete or NULL foreign key set on those child objects,
    despite the end-user not removing the child from the old
    association. [ticket:1764]

  - A collection lazy load will switch off default
    eagerloading on the reverse many-to-one side, since
    that loading is by definition unnecessary.  [ticket:1495]

  - Session.refresh() now does an equivalent expire()
    on the given instance first, so that the "refresh-expire"
    cascade is propagated.   Previously, refresh() was
    not affected in any way by the presence of "refresh-expire"
    cascade.   This is a change in behavior versus that
    of 0.6beta2, where the "lockmode" flag passed to refresh()
    would cause a version check to occur.  Since the instance
    is first expired, refresh() always upgrades the object
    to the most recent version.

  - The 'refresh-expire' cascade, when reaching a pending object,
    will expunge the object if the cascade also includes
    "delete-orphan", or will simply detach it otherwise.
    [ticket:1754]

  - id(obj) is no longer used internally within topological.py,
    as the sorting functions now require hashable objects
    only.  [ticket:1756]

  - The ORM will set the docstring of all generated descriptors
    to None by default.  This can be overridden using 'doc'
    (or if using Sphinx, attribute docstrings work too).

  - Added kw argument 'doc' to all mapper property callables
    as well as Column().  Will assemble the string 'doc' as
    the '__doc__' attribute on the descriptor.

  - Usage of version_id_col on a backend that supports
    cursor.rowcount for execute() but not executemany() now works
    when a delete is issued (already worked for saves, since those
    don't use executemany()). For a backend that doesn't support
    cursor.rowcount at all, a warning is emitted the same
    as with saves.  [ticket:1761]

  - The ORM now short-term caches the "compiled" form of
    insert() and update() constructs when flushing lists of
    objects of all the same class, thereby avoiding redundant
    compilation per individual INSERT/UPDATE within an
    individual flush() call.

  - internal getattr(), setattr(), getcommitted() methods
    on ColumnProperty, CompositeProperty, RelationshipProperty
    have been underscored (i.e. are private), signature has
    changed.

- engines
  - The C extension now also works with DBAPIs which use custom
    sequences as row (and not only tuples). [ticket:1757]

- sql
  - Restored some bind-labeling logic from 0.5 which ensures
    that tables with column names that overlap another column
    of the form "<tablename>_<columnname>" won't produce
    errors if column._label is used as a bind name during
    an UPDATE.  Test coverage which wasn't present in 0.5
    has been added.  [ticket:1755]

  - somejoin.select(fold_equivalents=True) is no longer
    deprecated, and will eventually be rolled into a more
    comprehensive version of the feature for [ticket:1729].

  - the Numeric type raises an *enormous* warning when expected
    to convert floats to Decimal from a DBAPI that returns floats.
    This includes SQLite, Sybase, MS-SQL. [ticket:1759]

  - Fixed an error in expression typing which caused an endless
    loop for expressions with two NULL types.

  - Fixed bug in execution_options() feature whereby the existing
    Transaction and other state information from the parent
    connection would not be propagated to the sub-connection.

  - Added new 'compiled_cache' execution option.  A dictionary
    where Compiled objects will be cached when the Connection
    compiles a clause expression into a dialect- and parameter-
    specific Compiled object.  It is the user's responsibility to
    manage the size of this dictionary, which will have keys
    corresponding to the dialect, clause element, the column
    names within the VALUES or SET clause of an INSERT or UPDATE,
    as well as the "batch" mode for an INSERT or UPDATE statement.

  - Added get_pk_constraint() to reflection.Inspector, similar
    to get_primary_keys() except returns a dict that includes the
    name of the constraint, for supported backends (PG so far).
    [ticket:1769]

  - Table.create() and Table.drop() no longer apply metadata-
    level create/drop events.  [ticket:1771]

- ext
  - the compiler extension now allows @compiles decorators
    on base classes that extend to child classes, @compiles
    decorators on child classes that aren't broken by a
    @compiles decorator on the base class.

  - Declarative will raise an informative error message
    if a non-mapped class attribute is referenced in the
    string-based relationship() arguments.

  - Further reworked the "mixin" logic in declarative to
    additionally allow __mapper_args__ as a @classproperty
    on a mixin, such as to dynamically assign polymorphic_identity.

- postgresql
  - Postgresql now reflects sequence names associated with
    SERIAL columns correctly, after the name of of the sequence
    has been changed.  Thanks to Kumar McMillan for the patch.
    [ticket:1071]

  - Repaired missing import in psycopg2._PGNumeric type when
    unknown numeric is received.

  - psycopg2/pg8000 dialects now aware of REAL[], FLOAT[],
    DOUBLE_PRECISION[], NUMERIC[] return types without
    raising an exception.

  - Postgresql reflects the name of primary key constraints,
    if one exists.  [ticket:1769]

- oracle
  - Now using cx_oracle output converters so that the
    DBAPI returns natively the kinds of values we prefer:
    - NUMBER values with positive precision + scale convert
      to cx_oracle.STRING and then to Decimal.   This
      allows perfect precision for the Numeric type when
      using cx_oracle.  [ticket:1759]
    - STRING/FIXED_CHAR now convert to unicode natively.
      SQLAlchemy's String types then don't need to
      apply any kind of conversions.

- firebird
   - The functionality of result.rowcount can be disabled on a
     per-engine basis by setting 'enable_rowcount=False'
     on create_engine().  Normally, cursor.rowcount is called
     after any UPDATE or DELETE statement unconditionally,
     because the cursor is then closed and Firebird requires
     an open cursor in order to get a rowcount.  This
     call is slightly expensive however so it can be disabled.
     To re-enable on a per-execution basis, the
     'enable_rowcount=True' execution option may be used.

- examples
  - Updated attribute_shard.py example to use a more robust
    method of searching a Query for binary expressions which
    compare columns against literal values.

0.6beta3
========

- orm
  - Major feature: Added new "subquery" loading capability to
    relationship().   This is an eager loading option which
    generates a second SELECT for each collection represented
    in a query, across all parents at once.  The query
    re-issues the original end-user query wrapped in a subquery,
    applies joins out to the target collection, and loads
    all those collections fully in one result, similar to
    "joined" eager loading but using all inner joins and not
    re-fetching full parent rows repeatedly (as most DBAPIs seem
    to do, even if columns are skipped).   Subquery loading is
    available at mapper config level using "lazy='subquery'" and
    at the query options level using "subqueryload(props..)",
    "subqueryload_all(props...)".  [ticket:1675]

  - To accomodate the fact that there are now two kinds of eager
    loading available, the new names for eagerload() and
    eagerload_all() are joinedload() and joinedload_all().  The
    old names will remain as synonyms for the foreseeable future.

  - The "lazy" flag on the relationship() function now accepts
    a string argument for all kinds of loading: "select", "joined",
    "subquery", "noload" and "dynamic", where the default is now
    "select".  The old values of True/
    False/None still retain their usual meanings and will remain
    as synonyms for the foreseeable future.

  - Added with_hint() method to Query() construct.  This calls
    directly down to select().with_hint() and also accepts
    entities as well as tables and aliases.  See with_hint() in the
    SQL section below. [ticket:921]

  - Fixed bug in Query whereby calling q.join(prop).from_self(...).
    join(prop) would fail to render the second join outside the
    subquery, when joining on the same criterion as was on the
    inside.

  - Fixed bug in Query whereby the usage of aliased() constructs
    would fail if the underlying table (but not the actual alias)
    were referenced inside the subquery generated by
    q.from_self() or q.select_from().

  - Fixed bug which affected all eagerload() and similar options
    such that "remote" eager loads, i.e. eagerloads off of a lazy
    load such as query(A).options(eagerload(A.b, B.c))
    wouldn't eagerload anything, but using eagerload("b.c") would
    work fine.

  - Query gains an add_columns(*columns) method which is a multi-
    version of add_column(col).  add_column(col) is future
    deprecated.

  - Query.join() will detect if the end result will be
    "FROM A JOIN A", and will raise an error if so.

  - Query.join(Cls.propname, from_joinpoint=True) will check more
    carefully that "Cls" is compatible with the current joinpoint,
    and act the same way as Query.join("propname", from_joinpoint=True)
    in that regard.

- sql
   - Added with_hint() method to select() construct.  Specify
     a table/alias, hint text, and optional dialect name, and
     "hints" will be rendered in the appropriate place in the
     statement.  Works for Oracle, Sybase, MySQL.  [ticket:921]

   - Fixed bug introduced in 0.6beta2 where column labels would
     render inside of column expressions already assigned a label.
     [ticket:1747]

- postgresql
   - The psycopg2 dialect will log NOTICE messages via the
     "sqlalchemy.dialects.postgresql" logger name.
     [ticket:877]

   - the TIME and TIMESTAMP types are now availble from the
     postgresql dialect directly, which add the PG-specific
     argument 'precision' to both.   'precision' and
     'timezone' are correctly reflected for both TIME and
     TIMEZONE types. [ticket:997]

- mysql
   - No longer guessing that TINYINT(1) should be BOOLEAN
     when reflecting - TINYINT(1) is returned.  Use Boolean/
     BOOLEAN in table definition to get boolean conversion
     behavior.  [ticket:1752]

- oracle
   - The Oracle dialect will issue VARCHAR type definitions
     using character counts, i.e. VARCHAR2(50 CHAR), so that
     the column is sized in terms of characters and not bytes.
     Column reflection of character types will also use
     ALL_TAB_COLUMNS.CHAR_LENGTH instead of
     ALL_TAB_COLUMNS.DATA_LENGTH.  Both of these behaviors take
     effect when the server version is 9 or higher - for
     version 8, the old behaviors are used.  [ticket:1744]

- declarative
   - Using a mixin won't break if the mixin implements an
     unpredictable __getattribute__(), i.e. Zope interfaces.
     [ticket:1746]

   - Using @classdecorator and similar on mixins to define
     __tablename__, __table_args__, etc. now works if
     the method references attributes on the ultimate
     subclass. [ticket:1749]

   - relationships and columns with foreign keys aren't
     allowed on declarative mixins, sorry.  [ticket:1751]

- ext
    - The sqlalchemy.orm.shard module now becomes an extension,
      sqlalchemy.ext.horizontal_shard.   The old import
      works with a deprecation warning.

0.6beta2
========

- py3k
  - Improved the installation/test setup regarding Python 3,
    now that Distribute runs on Py3k.   distribute_setup.py
    is now included.  See README.py3k for Python 3 installation/
    testing instructions.

- orm
  - The official name for the relation() function is now
    relationship(), to eliminate confusion over the relational
    algebra term.  relation() however will remain available
    in equal capacity for the foreseeable future.  [ticket:1740]

  - Added "version_id_generator" argument to Mapper, this is a
    callable that, given the current value of the "version_id_col",
    returns the next version number.  Can be used for alternate
    versioning schemes such as uuid, timestamps.  [ticket:1692]

  - added "lockmode" kw argument to Session.refresh(), will
    pass through the string value to Query the same as
    in with_lockmode(), will also do version check for a
    version_id_col-enabled mapping.

  - Fixed bug whereby calling query(A).join(A.bs).add_entity(B)
    in a joined inheritance scenario would double-add B as a
    target and produce an invalid query.  [ticket:1188]

  - Fixed bug in session.rollback() which involved not removing
    formerly "pending" objects from the session before
    re-integrating "deleted" objects, typically occured with
    natural primary keys. If there was a primary key conflict
    between them, the attach of the deleted would fail
    internally. The formerly "pending" objects are now expunged
    first. [ticket:1674]

  - Removed a lot of logging that nobody really cares about,
    logging that remains will respond to live changes in the
    log level.  No significant overhead is added.  [ticket:1719]

  - Fixed bug in session.merge() which prevented dict-like
    collections from merging.

  - session.merge() works with relations that specifically
    don't include "merge" in their cascade options - the target
    is ignored completely.

  - session.merge() will not expire existing scalar attributes
    on an existing target if the target has a value for that
    attribute, even if the incoming merged doesn't have
    a value for the attribute.  This prevents unnecessary loads
    on existing items.  Will still mark the attr as expired
    if the destination doesn't have the attr, though, which
    fulfills some contracts of deferred cols.  [ticket:1681]

  - The "allow_null_pks" flag is now called "allow_partial_pks",
    defaults to True, acts like it did in 0.5 again.  Except,
    it also is implemented within merge() such that a SELECT
    won't be issued for an incoming instance with partially
    NULL primary key if the flag is False.  [ticket:1680]

  - Fixed bug in 0.6-reworked "many-to-one" optimizations
    such that a many-to-one that is against a non-primary key
    column on the remote table (i.e. foreign key against a
    UNIQUE column) will pull the "old" value in from the
    database during a change, since if it's in the session
    we will need it for proper history/backref accounting,
    and we can't pull from the local identity map on a
    non-primary key column. [ticket:1737]

  - fixed internal error which would occur if calling has()
    or similar complex expression on a single-table inheritance
    relation(). [ticket:1731]

  - query.one() no longer applies LIMIT to the query, this to
    ensure that it fully counts all object identities present
    in the result, even in the case where joins may conceal
    multiple identities for two or more rows.  As a bonus,
    one() can now also be called with a query that issued
    from_statement() to start with since it no longer modifies
    the query.  [ticket:1688]

  - query.get() now returns None if queried for an identifier
    that is present in the identity map with a different class
    than the one requested, i.e. when using polymorphic loading.
    [ticket:1727]

  - A major fix in query.join(), when the "on" clause is an
    attribute of an aliased() construct, but there is already
    an existing join made out to a compatible target, query properly
    joins to the right aliased() construct instead of sticking
    onto the right side of the existing join.  [ticket:1706]

  - Slight improvement to the fix for [ticket:1362] to not issue
    needless updates of the primary key column during a so-called
    "row switch" operation, i.e. add + delete of two objects
    with the same PK.

  - Now uses sqlalchemy.orm.exc.DetachedInstanceError when an
    attribute load or refresh action fails due to object
    being detached from any Session.   UnboundExecutionError
    is specific to engines bound to sessions and statements.

  - Query called in the context of an expression will render
    disambiguating labels in all cases.    Note that this does
    not apply to the existing .statement and .subquery()
    accessor/method, which still honors the .with_labels()
    setting that defaults to False.

  - Query.union() retains disambiguating labels within the
    returned statement, thus avoiding various SQL composition
    errors which can result from column name conflicts.
    [ticket:1676]

  - Fixed bug in attribute history that inadvertently invoked
    __eq__ on mapped instances.

  - Some internal streamlining of object loading grants a
    small speedup for large results, estimates are around
    10-15%.   Gave the "state" internals a good solid
    cleanup with less complexity, datamembers,
    method calls, blank dictionary creates.

  - Documentation clarification for query.delete()
    [ticket:1689]

  - Fixed cascade bug in many-to-one relation() when attribute
    was set to None, introduced in r6711 (cascade deleted
    items into session during add()).

  - Calling query.order_by() or query.distinct() before calling
    query.select_from(), query.with_polymorphic(), or
    query.from_statement() raises an exception now instead of
    silently dropping those criterion. [ticket:1736]

  - query.scalar() now raises an exception if more than one
    row is returned.  All other behavior remains the same.
    [ticket:1735]

  - Fixed bug which caused "row switch" logic, that is an
    INSERT and DELETE replaced by an UPDATE, to fail when
    version_id_col was in use. [ticket:1692]

- sql
  - join() will now simulate a NATURAL JOIN by default.  Meaning,
    if the left side is a join, it will attempt to join the right
    side to the rightmost side of the left first, and not raise
    any exceptions about ambiguous join conditions if successful
    even if there are further join targets across the rest of
    the left.  [ticket:1714]

  - The most common result processors conversion function were
    moved to the new "processors" module.  Dialect authors are
    encouraged to use those functions whenever they correspond
    to their needs instead of implementing custom ones.

  - SchemaType and subclasses Boolean, Enum are now serializable,
    including their ddl listener and other event callables.
    [ticket:1694] [ticket:1698]

  - Some platforms will now interpret certain literal values
    as non-bind parameters, rendered literally into the SQL
    statement.   This to support strict SQL-92 rules that are
    enforced by some platforms including MS-SQL and Sybase.
    In this model, bind parameters aren't allowed in the
    columns clause of a SELECT, nor are certain ambiguous
    expressions like "?=?".  When this mode is enabled, the base
    compiler will render the binds as inline literals, but only across
    strings and numeric values.  Other types such as dates
    will raise an error, unless the dialect subclass defines
    a literal rendering function for those.  The bind parameter
    must have an embedded literal value already or an error
    is raised (i.e. won't work with straight bindparam('x')).
    Dialects can also expand upon the areas where binds are not
    accepted, such as within argument lists of functions
    (which don't work on MS-SQL when native SQL binding is used).

  - Added "unicode_errors" parameter to String, Unicode, etc.
    Behaves like the 'errors' keyword argument to
    the standard library's string.decode() functions.   This flag
    requires that `convert_unicode` is set to `"force"` - otherwise,
    SQLAlchemy is not guaranteed to handle the task of unicode
    conversion.   Note that this flag adds significant performance
    overhead to row-fetching operations for backends that already
    return unicode objects natively (which most DBAPIs do).  This
    flag should only be used as an absolute last resort for reading
    strings from a column with varied or corrupted encodings,
    which only applies to databases that accept invalid encodings
    in the first place (i.e. MySQL. *not* PG, Sqlite, etc.)

  - Added math negation operator support, -x.

  - FunctionElement subclasses are now directly executable the
    same way any func.foo() construct is, with automatic
    SELECT being applied when passed to execute().

  - The "type" and "bind" keyword arguments of a func.foo()
    construct are now local to "func." constructs and are
    not part of the FunctionElement base class, allowing
    a "type" to be handled in a custom constructor or
    class-level variable.

  - Restored the keys() method to ResultProxy.

  - The type/expression system now does a more complete job
    of determining the return type from an expression
    as well as the adaptation of the Python operator into
    a SQL operator, based on the full left/right/operator
    of the given expression.  In particular
    the date/time/interval system created for Postgresql
    EXTRACT in [ticket:1647] has now been generalized into
    the type system.   The previous behavior which often
    occured of an expression "column + literal" forcing
    the type of "literal" to be the same as that of "column"
    will now usually not occur - the type of
    "literal" is first derived from the Python type of the
    literal, assuming standard native Python types + date
    types, before falling back to that of the known type
    on the other side of the expression.  If the
    "fallback" type is compatible (i.e. CHAR from String),
    the literal side will use that.  TypeDecorator
    types override this by default to coerce the "literal"
    side unconditionally, which can be changed by implementing
    the coerce_compared_value() method. Also part of
    [ticket:1683].

  - Made sqlalchemy.sql.expressions.Executable part of public
    API, used for any expression construct that can be sent to
    execute().  FunctionElement now inherits Executable so that
    it gains execution_options(), which are also propagated
    to the select() that's generated within execute().
    Executable in turn subclasses _Generative which marks
    any ClauseElement that supports the @_generative
    decorator - these may also become "public" for the benefit
    of the compiler extension at some point.

  - A change to the solution for [ticket:1579] - an end-user
    defined bind parameter name that directly conflicts with
    a column-named bind generated directly from the SET or
    VALUES clause of an update/insert generates a compile error.
    This reduces call counts and eliminates some cases where
    undesirable name conflicts could still occur.

  - Column() requires a type if it has no foreign keys (this is
    not new).  An error is now raised if a Column() has no type
    and no foreign keys.  [ticket:1705]

  - the "scale" argument of the Numeric() type is honored when
    coercing a returned floating point value into a string
    on its way to Decimal - this allows accuracy to function
    on SQLite, MySQL.  [ticket:1717]

  - the copy() method of Column now copies over uninitialized
    "on table attach" events.  Helps with the new declarative
    "mixin" capability.

- engines
  - Added an optional C extension to speed up the sql layer by
    reimplementing RowProxy and the most common result processors.
    The actual speedups will depend heavily on your DBAPI and
    the mix of datatypes used in your tables, and can vary from
    a 30% improvement to more than 200%.  It also provides a modest
    (~15-20%) indirect improvement to ORM speed for large queries.
    Note that it is *not* built/installed by default.
    See README for installation instructions.

  - the execution sequence pulls all rowcount/last inserted ID
    info from the cursor before commit() is called on the
    DBAPI connection in an "autocommit" scenario.  This helps
    mxodbc with rowcount and is probably a good idea overall.

  - Opened up logging a bit such that isEnabledFor() is called
    more often, so that changes to the log level for engine/pool
    will be reflected on next connect.   This adds a small
    amount of method call overhead.  It's negligible and will make
    life a lot easier for all those situations when logging
    just happens to be configured after create_engine() is called.
    [ticket:1719]

  - The assert_unicode flag is deprecated.  SQLAlchemy will raise
    a warning in all cases where it is asked to encode a non-unicode
    Python string, as well as when a Unicode or UnicodeType type
    is explicitly passed a bytestring.  The String type will do nothing
    for DBAPIs that already accept Python unicode objects.

  - Bind parameters are sent as a tuple instead of a list. Some
    backend drivers will not accept bind parameters as a list.

  - threadlocal engine wasn't properly closing the connection
    upon close() - fixed that.

  - Transaction object doesn't rollback or commit if it isn't
    "active", allows more accurate nesting of begin/rollback/commit.

  - Python unicode objects as binds result in the Unicode type,
    not string, thus eliminating a certain class of unicode errors
    on drivers that don't support unicode binds.

  - Added "logging_name" argument to create_engine(), Pool() constructor
    as well as "pool_logging_name" argument to create_engine() which
    filters down to that of Pool.   Issues the given string name
    within the "name" field of logging messages instead of the default
    hex identifier string.  [ticket:1555]

  - The visit_pool() method of Dialect is removed, and replaced with
    connect().  This method returns a callable which receives
    the raw DBAPI connection after each one is created.   The callable
    is assembled into a first_connect/connect pool listener by the
    connection strategy if non-None.   Provides a simpler interface
    for dialects.

  - StaticPool now initializes, disposes and recreates without
    opening a new connection - the connection is only opened when
    first requested. dispose() also works on AssertionPool now.
    [ticket:1728]

- metadata
  - Added the ability to strip schema information when using
    "tometadata" by passing "schema=None" as an argument. If schema
    is not specified then the table's schema is retained.
    [ticket: 1673]

- declarative
  - DeclarativeMeta exclusively uses cls.__dict__ (not dict_)
    as the source of class information; _as_declarative exclusively
    uses the  dict_ passed to it as the source of class information
    (which when using DeclarativeMeta is cls.__dict__).  This should
    in theory make it easier for custom metaclasses to modify
    the state passed into _as_declarative.

  - declarative now accepts mixin classes directly, as a means
    to provide common functional and column-based elements on
    all subclasses, as well as a means to propagate a fixed
    set of __table_args__ or __mapper_args__ to subclasses.
    For custom combinations of __table_args__/__mapper_args__ from
    an inherited mixin to local, descriptors can now be used.
    New details are all up in the Declarative documentation.
    Thanks to Chris Withers for putting up with my strife
    on this. [ticket:1707]

  - the __mapper_args__ dict is copied when propagating to a subclass,
    and is taken straight off the class __dict__ to avoid any
    propagation from the parent.  mapper inheritance already
    propagates the things you want from the parent mapper.
    [ticket:1393]

  - An exception is raised when a single-table subclass specifies
    a column that is already present on the base class.
    [ticket:1732]

- mysql
  - Fixed reflection bug whereby when COLLATE was present,
    nullable flag and server defaults would not be reflected.
    [ticket:1655]

  - Fixed reflection of TINYINT(1) "boolean" columns defined with
    integer flags like UNSIGNED.

  - Further fixes for the mysql-connector dialect.  [ticket:1668]

  - Composite PK table on InnoDB where the "autoincrement" column
    isn't first will emit an explicit "KEY" phrase within
    CREATE TABLE thereby avoiding errors, [ticket:1496]

  - Added reflection/create table support for a wide range
    of MySQL keywords.  [ticket:1634]

  - Fixed import error which could occur reflecting tables on
    a Windows host [ticket:1580]

- mssql
  - Re-established support for the pymssql dialect.

  - Various fixes for implicit returning, reflection,
    etc. - the MS-SQL dialects aren't quite complete
    in 0.6 yet (but are close)

  - Added basic support for mxODBC [ticket:1710].

  - Removed the text_as_varchar option.

- oracle
   - "out" parameters require a type that is supported by
     cx_oracle.  An error will be raised if no cx_oracle
     type can be found.

   - Oracle 'DATE' now does not perform any result processing,
     as the DATE type in Oracle stores full date+time objects,
     that's what you'll get.  Note that the generic types.Date
     type *will* still call value.date() on incoming values,
     however.  When reflecting a table, the reflected type
     will be 'DATE'.

   - Added preliminary support for Oracle's WITH_UNICODE
     mode.  At the very least this establishes initial
     support for cx_Oracle with Python 3.  When WITH_UNICODE
     mode is used in Python 2.xx, a large and scary warning
     is emitted asking that the user seriously consider
     the usage of this difficult mode of operation.
     [ticket:1670]

   - The except_() method now renders as MINUS on Oracle,
     which is more or less equivalent on that platform.
     [ticket:1712]

   - Added support for rendering and reflecting
     TIMESTAMP WITH TIME ZONE, i.e. TIMESTAMP(timezone=True).
     [ticket:651]

   - Oracle INTERVAL type can now be reflected.

- sqlite
   - Added "native_datetime=True" flag to create_engine().
     This will cause the DATE and TIMESTAMP types to skip
     all bind parameter and result row processing, under
     the assumption that PARSE_DECLTYPES has been enabled
     on the connection.  Note that this is not entirely
     compatible with the "func.current_date()", which
     will be returned as a string. [ticket:1685]

- sybase
   - Implemented a preliminary working dialect for Sybase,
     with sub-implementations for Python-Sybase as well
     as Pyodbc.  Handles table
     creates/drops and basic round trip functionality.
     Does not yet include reflection or comprehensive
     support of unicode/special expressions/etc.

- examples
   - Changed the beaker cache example a bit to have a separate
     RelationCache option for lazyload caching.  This object
     does a lookup among any number of potential attributes
     more efficiently by grouping several into a common structure.
     Both FromCache and RelationCache are simpler individually.

- documentation
   - Major cleanup work in the docs to link class, function, and
     method names into the API docs. [ticket:1700/1702/1703]

0.6beta1
========
- Major Release
  - For the full set of feature descriptions, see
    http://www.sqlalchemy.org/trac/wiki/06Migration .
    This document is a work in progress.

  - All bug fixes and feature enhancements from the most
    recent 0.5 version and below are also included within 0.6.

  - Platforms targeted now include Python 2.4/2.5/2.6, Python
    3.1, Jython2.5.

- orm
  - Changes to query.update() and query.delete():
      - the 'expire' option on query.update() has been renamed to
        'fetch', thus matching that of query.delete().
        'expire' is deprecated and issues a warning.

      - query.update() and query.delete() both default to
        'evaluate' for the synchronize strategy.

      - the 'synchronize' strategy for update() and delete()
        raises an error on failure. There is no implicit fallback
        onto "fetch". Failure of evaluation is based on the
        structure of criteria, so success/failure is deterministic
        based on code structure.

  - Enhancements on many-to-one relations:
      - many-to-one relations now fire off a lazyload in fewer
        cases, including in most cases will not fetch the "old"
        value when a new one is replaced.

      - many-to-one relation to a joined-table subclass now uses
        get() for a simple load (known as the "use_get"
        condition), i.e. Related->Sub(Base), without the need to
        redefine the primaryjoin condition in terms of the base
        table. [ticket:1186]

      - specifying a foreign key with a declarative column, i.e.
        ForeignKey(MyRelatedClass.id) doesn't break the "use_get"
        condition from taking place [ticket:1492]

      - relation(), eagerload(), and eagerload_all() now feature
        an option called "innerjoin". Specify `True` or `False` to
        control whether an eager join is constructed as an INNER
        or OUTER join. Default is `False` as always. The mapper
        options will override whichever setting is specified on
        relation(). Should generally be set for many-to-one, not
        nullable foreign key relations to allow improved join
        performance. [ticket:1544]

      - the behavior of eagerloading such that the main query is
        wrapped in a subquery when LIMIT/OFFSET are present now
        makes an exception for the case when all eager loads are
        many-to-one joins. In those cases, the eager joins are
        against the parent table directly along with the
        limit/offset without the extra overhead of a subquery,
        since a many-to-one join does not add rows to the result.

  - Enhancements / Changes on Session.merge():
     - the "dont_load=True" flag on Session.merge() is deprecated
       and is now "load=False".

     - Session.merge() is performance optimized, using half the
       call counts for "load=False" mode compared to 0.5 and
       significantly fewer SQL queries in the case of collections
       for "load=True" mode.

     - merge() will not issue a needless merge of attributes if the
       given instance is the same instance which is already present.

     - merge() now also merges the "options" associated with a given
       state, i.e. those passed through query.options() which follow
       along with an instance, such as options to eagerly- or
       lazyily- load various attributes.   This is essential for
       the construction of highly integrated caching schemes.  This
       is a subtle behavioral change vs. 0.5.

     - A bug was fixed regarding the serialization of the "loader
       path" present on an instance's state, which is also necessary
       when combining the usage of merge() with serialized state
       and associated options that should be preserved.

     - The all new merge() is showcased in a new comprehensive
       example of how to integrate Beaker with SQLAlchemy.  See
       the notes in the "examples" note below.

  - Primary key values can now be changed on a joined-table inheritance
    object, and ON UPDATE CASCADE will be taken into account when
    the flush happens.  Set the new "passive_updates" flag to False
    on mapper() when using SQLite or MySQL/MyISAM. [ticket:1362]

  - flush() now detects when a primary key column was updated by
    an ON UPDATE CASCADE operation from another primary key, and
    can then locate the row for a subsequent UPDATE on the new PK
    value.  This occurs when a relation() is there to establish
    the relationship as well as passive_updates=True.  [ticket:1671]

  - the "save-update" cascade will now cascade the pending *removed*
    values from a scalar or collection attribute into the new session
    during an add() operation.  This so that the flush() operation
    will also delete or modify rows of those disconnected items.

  - Using a "dynamic" loader with a "secondary" table now produces
    a query where the "secondary" table is *not* aliased.  This
    allows the secondary Table object to be used in the "order_by"
    attribute of the relation(), and also allows it to be used
    in filter criterion against the dynamic relation.
    [ticket:1531]

  - relation() with uselist=False will emit a warning when
    an eager or lazy load locates more than one valid value for
    the row.  This may be due to primaryjoin/secondaryjoin
    conditions which aren't appropriate for an eager LEFT OUTER
    JOIN or for other conditions.  [ticket:1643]

  - an explicit check occurs when a synonym() is used with
    map_column=True, when a ColumnProperty (deferred or otherwise)
    exists separately in the properties dictionary sent to mapper
    with the same keyname.   Instead of silently replacing
    the existing property (and possible options on that property),
    an error is raised.  [ticket:1633]

  - a "dynamic" loader sets up its query criterion at construction
    time so that the actual query is returned from non-cloning
    accessors like "statement".

  - the "named tuple" objects returned when iterating a
    Query() are now pickleable.

  - mapping to a select() construct now requires that you
    make an alias() out of it distinctly.   This to eliminate
    confusion over such issues as [ticket:1542]

  - query.join() has been reworked to provide more consistent
    behavior and more flexibility (includes [ticket:1537])

  - query.select_from() accepts multiple clauses to produce
    multiple comma separated entries within the FROM clause.
    Useful when selecting from multiple-homed join() clauses.

  - query.select_from() also accepts mapped classes, aliased()
    constructs, and mappers as arguments.  In particular this
    helps when querying from multiple joined-table classes to ensure
    the full join gets rendered.

  - query.get() can be used with a mapping to an outer join
    where one or more of the primary key values are None.
    [ticket:1135]

  - query.from_self(), query.union(), others which do a
    "SELECT * from (SELECT...)" type of nesting will do
    a better job translating column expressions within the subquery
    to the columns clause of the outer query.  This is
    potentially backwards incompatible with 0.5, in that this
    may break queries with literal expressions that do not have labels
    applied (i.e. literal('foo'), etc.)
    [ticket:1568]

  - relation primaryjoin and secondaryjoin now check that they
    are column-expressions, not just clause elements.  this prohibits
    things like FROM expressions being placed there directly.
    [ticket:1622]

  - `expression.null()` is fully understood the same way
    None is when comparing an object/collection-referencing
    attribute within query.filter(), filter_by(), etc.
    [ticket:1415]

  - added "make_transient()" helper function which transforms a
    persistent/ detached instance into a transient one (i.e.
    deletes the instance_key and removes from any session.)
    [ticket:1052]

  - the allow_null_pks flag on mapper() is deprecated, and
    the feature is turned "on" by default.  This means that
    a row which has a non-null value for any of its primary key
    columns will be considered an identity.  The need for this
    scenario typically only occurs when mapping to an outer join.
    [ticket:1339]

   - the mechanics of "backref" have been fully merged into the
     finer grained "back_populates" system, and take place entirely
     within the _generate_backref() method of RelationProperty.  This
     makes the initialization procedure of RelationProperty
     simpler and allows easier propagation of settings (such as from
     subclasses of RelationProperty) into the reverse reference.
     The internal BackRef() is gone and backref() returns a plain
     tuple that is understood by RelationProperty.

   - The version_id_col feature on mapper() will raise a warning when
     used with dialects that don't support "rowcount" adequately.
     [ticket:1569]

   - added "execution_options()" to Query, to so options can be
     passed to the resulting statement. Currently only
     Select-statements have these options, and the only option
     used is "stream_results", and the only dialect which knows
     "stream_results" is psycopg2.

   - Query.yield_per() will set the "stream_results" statement
     option automatically.

   - Deprecated or removed:
      * 'allow_null_pks' flag on mapper() is deprecated.  It does
        nothing now and the setting is "on" in all cases.
      * 'transactional' flag on sessionmaker() and others is
        removed. Use 'autocommit=True' to indicate 'transactional=False'.
      * 'polymorphic_fetch' argument on mapper() is removed.
        Loading can be controlled using the 'with_polymorphic'
        option.
      * 'select_table' argument on mapper() is removed.  Use
        'with_polymorphic=("*", <some selectable>)' for this
        functionality.
      * 'proxy' argument on synonym() is removed.  This flag
        did nothing throughout 0.5, as the "proxy generation"
        behavior is now automatic.
      * Passing a single list of elements to eagerload(),
        eagerload_all(), contains_eager(), lazyload(),
        defer(), and undefer() instead of multiple positional
        *args is deprecated.
      * Passing a single list of elements to query.order_by(),
        query.group_by(), query.join(), or query.outerjoin()
        instead of multiple positional *args is deprecated.
      * query.iterate_instances() is removed.  Use query.instances().
      * Query.query_from_parent() is removed.  Use the
        sqlalchemy.orm.with_parent() function to produce a
        "parent" clause, or alternatively query.with_parent().
      * query._from_self() is removed, use query.from_self()
        instead.
      * the "comparator" argument to composite() is removed.
        Use "comparator_factory".
      * RelationProperty._get_join() is removed.
      * the 'echo_uow' flag on Session is removed.  Use
        logging on the "sqlalchemy.orm.unitofwork" name.
      * session.clear() is removed.  use session.expunge_all().
      * session.save(), session.update(), session.save_or_update()
        are removed.  Use session.add() and session.add_all().
      * the "objects" flag on session.flush() remains deprecated.
      * the "dont_load=True" flag on session.merge() is deprecated
        in favor of "load=False".
      * ScopedSession.mapper remains deprecated.  See the
        usage recipe at
        http://www.sqlalchemy.org/trac/wiki/UsageRecipes/SessionAwareMapper
      * passing an InstanceState (internal SQLAlchemy state object) to
        attributes.init_collection() or attributes.get_history() is
        deprecated.  These functions are public API and normally
        expect a regular mapped object instance.
      * the 'engine' parameter to declarative_base() is removed.
        Use the 'bind' keyword argument.

- sql

    - the "autocommit" flag on select() and text() as well
      as select().autocommit() are deprecated - now call
      .execution_options(autocommit=True) on either of those
      constructs, also available directly on Connection and orm.Query.

    - the autoincrement flag on column now indicates the column
      which should be linked to cursor.lastrowid, if that method
      is used.  See the API docs for details.

    - an executemany() now requires that all bound parameter
      sets require that all keys are present which are
      present in the first bound parameter set.  The structure
      and behavior of an insert/update statement is very much
      determined by the first parameter set, including which
      defaults are going to fire off, and a minimum of
      guesswork is performed with all the rest so that performance
      is not impacted.  For this reason defaults would otherwise
      silently "fail" for missing parameters, so this is now guarded
      against. [ticket:1566]

    - returning() support is native to insert(), update(),
      delete(). Implementations of varying levels of
      functionality exist for Postgresql, Firebird, MSSQL and
      Oracle. returning() can be called explicitly with column
      expressions which are then returned in the resultset,
      usually via fetchone() or first().

      insert() constructs will also use RETURNING implicitly to
      get newly generated primary key values, if the database
      version in use supports it (a version number check is
      performed). This occurs if no end-user returning() was
      specified.

    - union(), intersect(), except() and other "compound" types
      of statements have more consistent behavior w.r.t.
      parenthesizing.   Each compound element embedded within
      another will now be grouped with parenthesis - previously,
      the first compound element in the list would not be grouped,
      as SQLite doesn't like a statement to start with
      parenthesis.   However, Postgresql in particular has
      precedence rules regarding INTERSECT, and it is
      more consistent for parenthesis to be applied equally
      to all sub-elements.   So now, the workaround for SQLite
      is also what the workaround for PG was previously -
      when nesting compound elements, the first one usually needs
      ".alias().select()" called on it to wrap it inside
      of a subquery.  [ticket:1665]

    - insert() and update() constructs can now embed bindparam()
      objects using names that match the keys of columns.  These
      bind parameters will circumvent the usual route to those
      keys showing up in the VALUES or SET clause of the generated
      SQL. [ticket:1579]

    - the Binary type now returns data as a Python string
      (or a "bytes" type in Python 3), instead of the built-
      in "buffer" type.  This allows symmetric round trips
      of binary data. [ticket:1524]

    - Added a tuple_() construct, allows sets of expressions
      to be compared to another set, typically with IN against
      composite primary keys or similar.  Also accepts an
      IN with multiple columns.   The "scalar select can
      have only one column" error message is removed - will
      rely upon the database to report problems with
      col mismatch.

    - User-defined "default" and "onupdate" callables which
      accept a context should now call upon
      "context.current_parameters" to get at the dictionary
      of bind parameters currently being processed.  This
      dict is available in the same way regardless of
      single-execute or executemany-style statement execution.

    - multi-part schema names, i.e. with dots such as
      "dbo.master", are now rendered in select() labels
      with underscores for dots, i.e. "dbo_master_table_column".
      This is a "friendly" label that behaves better
      in result sets. [ticket:1428]

    - removed needless "counter" behavior with select()
      labelnames that match a column name in the table,
      i.e. generates "tablename_id" for "id", instead of
      "tablename_id_1" in an attempt to avoid naming
      conflicts, when the table has a column actually
      named "tablename_id" - this is because
      the labeling logic is always applied to all columns
      so a naming conflict will never occur.

    - calling expr.in_([]), i.e. with an empty list, emits a warning
      before issuing the usual "expr != expr" clause.  The
      "expr != expr" can be very expensive, and it's preferred
      that the user not issue in_() if the list is empty,
      instead simply not querying, or modifying the criterion
       as appropriate for more complex situations.
       [ticket:1628]

    - Added "execution_options()" to select()/text(), which set the
      default options for the Connection.  See the note in "engines".

    - Deprecated or removed:
        * "scalar" flag on select() is removed, use
          select.as_scalar().
        * "shortname" attribute on bindparam() is removed.
        * postgres_returning, firebird_returning flags on
          insert(), update(), delete() are deprecated, use
          the new returning() method.
        * fold_equivalents flag on join is deprecated (will remain
          until [ticket:1131] is implemented)

- engines
  - transaction isolation level may be specified with
    create_engine(... isolation_level="..."); available on
    postgresql and sqlite. [ticket:443]

  - Connection has execution_options(), generative method
    which accepts keywords that affect how the statement
    is executed w.r.t. the DBAPI.   Currently supports
    "stream_results", causes psycopg2 to use a server
    side cursor for that statement, as well as
    "autocommit", which is the new location for the "autocommit"
    option from select() and text().   select() and
    text() also have .execution_options() as well as
    ORM Query().

  - fixed the import for entrypoint-driven dialects to
    not rely upon silly tb_info trick to determine import
    error status.  [ticket:1630]

  - added first() method to ResultProxy, returns first row and
    closes result set immediately.

  - RowProxy objects are now pickleable, i.e. the object returned
    by result.fetchone(), result.fetchall() etc.

  - RowProxy no longer has a close() method, as the row no longer
    maintains a reference to the parent.  Call close() on
    the parent ResultProxy instead, or use autoclose.

  - ResultProxy internals have been overhauled to greatly reduce
    method call counts when fetching columns.  Can provide a large
    speed improvement (up to more than 100%) when fetching large
    result sets.  The improvement is larger when fetching columns
    that have no type-level processing applied and when using
    results as tuples (instead of as dictionaries).  Many
    thanks to Elixir's Gaëtan de Menten for this dramatic
    improvement !  [ticket:1586]

  - Databases which rely upon postfetch of "last inserted id"
    to get at a generated sequence value (i.e. MySQL, MS-SQL)
    now work correctly when there is a composite primary key
    where the "autoincrement" column is not the first primary
    key column in the table.

  - the last_inserted_ids() method has been renamed to the
    descriptor "inserted_primary_key".

  - setting echo=False on create_engine() now sets the loglevel
    to WARN instead of NOTSET.  This so that logging can be
    disabled for a particular engine even if logging
    for "sqlalchemy.engine" is enabled overall.  Note that the
    default setting of "echo" is `None`. [ticket:1554]

  - ConnectionProxy now has wrapper methods for all transaction
    lifecycle events, including begin(), rollback(), commit()
    begin_nested(), begin_prepared(), prepare(), release_savepoint(),
    etc.

  - Connection pool logging now uses both INFO and DEBUG
    log levels for logging.  INFO is for major events such
    as invalidated connections, DEBUG for all the acquire/return
    logging.  `echo_pool` can be False, None, True or "debug"
    the same way as `echo` works.

  - All pyodbc-dialects now support extra pyodbc-specific
    kw arguments 'ansi', 'unicode_results', 'autocommit'.
    [ticket:1621]

  - the "threadlocal" engine has been rewritten and simplified
    and now supports SAVEPOINT operations.

  - deprecated or removed
      * result.last_inserted_ids() is deprecated.  Use
        result.inserted_primary_key
      * dialect.get_default_schema_name(connection) is now
        public via dialect.default_schema_name.
      * the "connection" argument from engine.transaction() and
        engine.run_callable() is removed - Connection itself
        now has those methods.   All four methods accept
        *args and **kwargs which are passed to the given callable,
        as well as the operating connection.

- schema
    - the `__contains__()` method of `MetaData` now accepts
      strings or `Table` objects as arguments.  If given
      a `Table`, the argument is converted to `table.key` first,
      i.e. "[schemaname.]<tablename>" [ticket:1541]

    - deprecated MetaData.connect() and
      ThreadLocalMetaData.connect() have been removed - send
      the "bind" attribute to bind a metadata.

    - deprecated metadata.table_iterator() method removed (use
      sorted_tables)

    - deprecated PassiveDefault - use DefaultClause.

    - the "metadata" argument is removed from DefaultGenerator
      and subclasses, but remains locally present on Sequence,
      which is a standalone construct in DDL.

    - Removed public mutability from Index and Constraint
      objects:
        - ForeignKeyConstraint.append_element()
        - Index.append_column()
        - UniqueConstraint.append_column()
        - PrimaryKeyConstraint.add()
        - PrimaryKeyConstraint.remove()
      These should be constructed declaratively (i.e. in one
      construction).

    - The "start" and "increment" attributes on Sequence now
      generate "START WITH" and "INCREMENT BY" by default,
      on Oracle and Postgresql.  Firebird doesn't support
      these keywords right now.  [ticket:1545]

    - UniqueConstraint, Index, PrimaryKeyConstraint all accept
      lists of column names or column objects as arguments.

    - Other removed things:
        - Table.key (no idea what this was for)
        - Table.primary_key is not assignable - use
          table.append_constraint(PrimaryKeyConstraint(...))
        - Column.bind       (get via column.table.bind)
        - Column.metadata   (get via column.table.metadata)
        - Column.sequence   (use column.default)
        - ForeignKey(constraint=some_parent) (is now private _constraint)

    - The use_alter flag on ForeignKey is now a shortcut option
      for operations that can be hand-constructed using the
      DDL() event system. A side effect of this refactor is
      that ForeignKeyConstraint objects with use_alter=True
      will *not* be emitted on SQLite, which does not support
      ALTER for foreign keys.

    - ForeignKey and ForeignKeyConstraint objects now correctly
      copy() all their public keyword arguments.  [ticket:1605]

- Reflection/Inspection
    - Table reflection has been expanded and generalized into
      a new API called "sqlalchemy.engine.reflection.Inspector".
      The Inspector object provides fine-grained information about
      a wide variety of schema information, with room for expansion,
      including table names, column names, view definitions, sequences,
      indexes, etc.

    - Views are now reflectable as ordinary Table objects.  The same
      Table constructor is used, with the caveat that "effective"
      primary and foreign key constraints aren't part of the reflection
      results; these have to be specified explicitly if desired.

    - The existing autoload=True system now uses Inspector underneath
      so that each dialect need only return "raw" data about tables
      and other objects - Inspector is the single place that information
      is compiled into Table objects so that consistency is at a maximum.

- DDL
    - the DDL system has been greatly expanded.  the DDL() class
      now extends the more generic DDLElement(), which forms the basis
      of many new constructs:

        - CreateTable()
        - DropTable()
        - AddConstraint()
        - DropConstraint()
        - CreateIndex()
        - DropIndex()
        - CreateSequence()
        - DropSequence()

       These support "on" and "execute-at()" just like plain DDL()
       does.  User-defined DDLElement subclasses can be created and
       linked to a compiler using the sqlalchemy.ext.compiler extension.

    - The signature of the "on" callable passed to DDL() and
      DDLElement() is revised as follows:

        "ddl" - the DDLElement object itself.
        "event" - the string event name.
        "target" - previously "schema_item", the Table or
        MetaData object triggering the event.
        "connection" - the Connection object in use for the operation.
        **kw - keyword arguments.  In the case of MetaData before/after
          create/drop, the list of Table objects for which
          CREATE/DROP DDL is to be issued is passed as the kw
          argument "tables". This is necessary for metadata-level
          DDL that is dependent on the presence of specific tables.

      - the "schema_item" attribute of DDL has been renamed to
        "target".

- dialect refactor
    - Dialect modules are now broken into database dialects
      plus DBAPI implementations. Connect URLs are now
      preferred to be specified using dialect+driver://...,
      i.e. "mysql+mysqldb://scott:tiger@localhost/test". See
      the 0.6 documentation for examples.

    - the setuptools entrypoint for external dialects is now
      called "sqlalchemy.dialects".

    - the "owner" keyword argument is removed from Table. Use
      "schema" to represent any namespaces to be prepended to
      the table name.

    - server_version_info becomes a static attribute.

    - dialects receive an initialize() event on initial
      connection to determine connection properties.

    - dialects receive a visit_pool event have an opportunity
      to establish pool listeners.

    - cached TypeEngine classes are cached per-dialect class
      instead of per-dialect.

    - new UserDefinedType should be used as a base class for
      new types, which preserves the 0.5 behavior of
      get_col_spec().

    - The result_processor() method of all type classes now
      accepts a second argument "coltype", which is the DBAPI
      type argument from cursor.description.  This argument
      can help some types decide on the most efficient processing
      of result values.

    - Deprecated Dialect.get_params() removed.

    - Dialect.get_rowcount() has been renamed to a descriptor
      "rowcount", and calls cursor.rowcount directly. Dialects
      which need to hardwire a rowcount in for certain calls
      should override the method to provide different behavior.

    - DefaultRunner and subclasses have been removed.  The job
      of this object has been simplified and moved into
      ExecutionContext.  Dialects which support sequences should
      add a `fire_sequence()` method to their execution context
      implementation.  [ticket:1566]

    - Functions and operators generated by the compiler now use
      (almost) regular dispatch functions of the form
      "visit_<opname>" and "visit_<funcname>_fn" to provide
      customed processing. This replaces the need to copy the
      "functions" and "operators" dictionaries in compiler
      subclasses with straightforward visitor methods, and also
      allows compiler subclasses complete control over
      rendering, as the full _Function or _BinaryExpression
      object is passed in.

- postgresql
    - New dialects: pg8000, zxjdbc, and pypostgresql
      on py3k.

    - The "postgres" dialect is now named "postgresql" !
      Connection strings look like:

           postgresql://scott:tiger@localhost/test
           postgresql+pg8000://scott:tiger@localhost/test

       The "postgres" name remains for backwards compatiblity
       in the following ways:

           - There is a "postgres.py" dummy dialect which
             allows old URLs to work, i.e.
             postgres://scott:tiger@localhost/test

           - The "postgres" name can be imported from the old
             "databases" module, i.e. "from
             sqlalchemy.databases import postgres" as well as
             "dialects", "from sqlalchemy.dialects.postgres
             import base as pg", will send a deprecation
             warning.

           - Special expression arguments are now named
             "postgresql_returning" and "postgresql_where", but
             the older "postgres_returning" and
             "postgres_where" names still work with a
             deprecation warning.

    - "postgresql_where" now accepts SQL expressions which
      can also include literals, which will be quoted as needed.

    - The psycopg2 dialect now uses psycopg2's "unicode extension"
      on all new connections, which allows all String/Text/etc.
      types to skip the need to post-process bytestrings into
      unicode (an expensive step due to its volume).  Other
      dialects which return unicode natively (pg8000, zxjdbc)
      also skip unicode post-processing.

    - Added new ENUM type, which exists as a schema-level
      construct and extends the generic Enum type.  Automatically
      associates itself with tables and their parent metadata
      to issue the appropriate CREATE TYPE/DROP TYPE
      commands as needed, supports unicode labels, supports
      reflection.  [ticket:1511]

    - INTERVAL supports an optional "precision" argument
      corresponding to the argument that PG accepts.

    - using new dialect.initialize() feature to set up
      version-dependent behavior.

    - somewhat better support for % signs in table/column names;
      psycopg2 can't handle a bind parameter name of
      %(foobar)s however and SQLA doesn't want to add overhead
      just to treat that one non-existent use case.
      [ticket:1279]

    - Inserting NULL into a primary key + foreign key column
      will allow the "not null constraint" error to raise,
      not an attempt to execute a nonexistent "col_id_seq"
      sequence.  [ticket:1516]

    - autoincrement SELECT statements, i.e. those which
      select from a procedure that modifies rows, now work
      with server-side cursor mode (the named cursor isn't
      used for such statements.)

    - postgresql dialect can properly detect pg "devel" version
      strings, i.e. "8.5devel" [ticket:1636]

    - The psycopg2 now respects the statement option
      "stream_results". This option overrides the connection setting
      "server_side_cursors". If true, server side cursors will be
      used for the statement. If false, they will not be used, even
      if "server_side_cursors" is true on the
      connection. [ticket:1619]

- mysql
    - New dialects: oursql, a new native dialect,
      MySQL Connector/Python, a native Python port of MySQLdb,
      and of course zxjdbc on Jython.

    - VARCHAR/NVARCHAR will not render without a length, raises
      an error before passing to MySQL.   Doesn't impact
      CAST since VARCHAR is not allowed in MySQL CAST anyway,
      the dialect renders CHAR/NCHAR in those cases.

    - all the _detect_XXX() functions now run once underneath
      dialect.initialize()

    - somewhat better support for % signs in table/column names;
      MySQLdb can't handle % signs in SQL when executemany() is used,
      and SQLA doesn't want to add overhead just to treat that one
      non-existent use case. [ticket:1279]

    - the BINARY and MSBinary types now generate "BINARY" in all
      cases.  Omitting the "length" parameter will generate
      "BINARY" with no length.  Use BLOB to generate an unlengthed
      binary column.

    - the "quoting='quoted'" argument to MSEnum/ENUM is deprecated.
      It's best to rely upon the automatic quoting.

    - ENUM now subclasses the new generic Enum type, and also handles
      unicode values implicitly, if the given labelnames are unicode
      objects.

    - a column of type TIMESTAMP now defaults to NULL if
      "nullable=False" is not passed to Column(), and no default
      is present. This is now consistent with all other types,
      and in the case of TIMESTAMP explictly renders "NULL"
      due to MySQL's "switching" of default nullability
      for TIMESTAMP columns. [ticket:1539]

- oracle
    - unit tests pass 100% with cx_oracle !

    - support for cx_Oracle's "native unicode" mode which does
      not require NLS_LANG to be set. Use the latest 5.0.2 or
      later of cx_oracle.

    - an NCLOB type is added to the base types.

    - use_ansi=False won't leak into the FROM/WHERE clause of
      a statement that's selecting from a subquery that also
      uses JOIN/OUTERJOIN.

    - added native INTERVAL type to the dialect.  This supports
      only the DAY TO SECOND interval type so far due to lack
      of support in cx_oracle for YEAR TO MONTH. [ticket:1467]

    - usage of the CHAR type results in cx_oracle's
      FIXED_CHAR dbapi type being bound to statements.

    - the Oracle dialect now features NUMBER which intends
      to act justlike Oracle's NUMBER type.  It is the primary
      numeric type returned by table reflection and attempts
      to return Decimal()/float/int based on the precision/scale
      parameters.  [ticket:885]

    - func.char_length is a generic function for LENGTH

    - ForeignKey() which includes onupdate=<value> will emit a
      warning, not emit ON UPDATE CASCADE which is unsupported
      by oracle

    - the keys() method of RowProxy() now returns the result
      column names *normalized* to be SQLAlchemy case
      insensitive names. This means they will be lower case for
      case insensitive names, whereas the DBAPI would normally
      return them as UPPERCASE names. This allows row keys() to
      be compatible with further SQLAlchemy operations.

    - using new dialect.initialize() feature to set up
      version-dependent behavior.

    - using types.BigInteger with Oracle will generate
      NUMBER(19) [ticket:1125]

    - "case sensitivity" feature will detect an all-lowercase
      case-sensitive column name during reflect and add
      "quote=True" to the generated Column, so that proper
      quoting is maintained.

- firebird
    - the keys() method of RowProxy() now returns the result
      column names *normalized* to be SQLAlchemy case
      insensitive names. This means they will be lower case for
      case insensitive names, whereas the DBAPI would normally
      return them as UPPERCASE names. This allows row keys() to
      be compatible with further SQLAlchemy operations.

    - using new dialect.initialize() feature to set up
      version-dependent behavior.

    - "case sensitivity" feature will detect an all-lowercase
      case-sensitive column name during reflect and add
      "quote=True" to the generated Column, so that proper
      quoting is maintained.

- mssql
    - MSSQL + Pyodbc + FreeTDS now works for the most part,
      with possible exceptions regarding binary data as well as
      unicode schema identifiers.
    - the "has_window_funcs" flag is removed. LIMIT/OFFSET
      usage will use ROW NUMBER as always, and if on an older
      version of SQL Server, the operation fails. The behavior
      is exactly the same except the error is raised by SQL
      server instead of the dialect, and no flag setting is
      required to enable it.
    - the "auto_identity_insert" flag is removed. This feature
      always takes effect when an INSERT statement overrides a
      column that is known to have a sequence on it. As with
      "has_window_funcs", if the underlying driver doesn't
      support this, then you can't do this operation in any
      case, so there's no point in having a flag.
    - using new dialect.initialize() feature to set up
      version-dependent behavior.
    - removed references to sequence which is no longer used.
      implicit identities in mssql work the same as implicit
      sequences on any other dialects. Explicit sequences are
      enabled through the use of "default=Sequence()". See
      the MSSQL dialect documentation for more information.

- sqlite
    - DATE, TIME and DATETIME types can now take optional storage_format
      and regexp argument. storage_format can be used to store those types
      using a custom string format. regexp allows to use a custom regular
      expression to match string values from the database.
    - Time and DateTime types now use by a default a stricter regular
      expression to match strings from the database. Use the regexp
      argument if you are using data stored in a legacy format.
    - __legacy_microseconds__ on SQLite Time and DateTime types is not
      supported anymore. You should use the storage_format argument
      instead.
    - Date, Time and DateTime types are now stricter in what they accept as
      bind parameters: Date type only accepts date objects (and datetime
      ones, because they inherit from date), Time only accepts time
      objects, and DateTime only accepts date and datetime objects.
    - Table() supports a keyword argument "sqlite_autoincrement", which
      applies the SQLite keyword "AUTOINCREMENT" to the single integer
      primary key column when generating DDL. Will prevent generation of
      a separate PRIMARY KEY constraint. [ticket:1016]

- new dialects
    - postgresql+pg8000
    - postgresql+pypostgresql (partial)
    - postgresql+zxjdbc
    - mysql+pyodbc
    - mysql+zxjdbc

- types
    - The construction of types within dialects has been totally
      overhauled.  Dialects now define publically available types
      as UPPERCASE names exclusively, and internal implementation
      types using underscore identifiers (i.e. are private).
      The system by which types are expressed in SQL and DDL
      has been moved to the compiler system.  This has the
      effect that there are much fewer type objects within
      most dialects. A detailed document on this architecture
      for dialect authors is in
      lib/sqlalchemy/dialects/type_migration_guidelines.txt .

    - Types no longer make any guesses as to default
      parameters. In particular, Numeric, Float, NUMERIC,
      FLOAT, DECIMAL don't generate any length or scale unless
      specified.

    - types.Binary is renamed to types.LargeBinary, it only
      produces BLOB, BYTEA, or a similar "long binary" type.
      New base BINARY and VARBINARY
      types have been added to access these MySQL/MS-SQL specific
      types in an agnostic way [ticket:1664].

    - String/Text/Unicode types now skip the unicode() check
      on each result column value if the dialect has
      detected the DBAPI as returning Python unicode objects
      natively.  This check is issued on first connect
      using "SELECT CAST 'some text' AS VARCHAR(10)" or
      equivalent, then checking if the returned object
      is a Python unicode.   This allows vast performance
      increases for native-unicode DBAPIs, including
      pysqlite/sqlite3, psycopg2, and pg8000.

    - Most types result processors have been checked for possible speed
      improvements. Specifically, the following generic types have been
      optimized, resulting in varying speed improvements:
      Unicode, PickleType, Interval, TypeDecorator, Binary.
      Also the following dbapi-specific implementations have been improved:
      Time, Date and DateTime on Sqlite, ARRAY on Postgresql,
      Time on MySQL, Numeric(as_decimal=False) on MySQL, oursql and
      pypostgresql, DateTime on cx_oracle and LOB-based types on cx_oracle.

    - Reflection of types now returns the exact UPPERCASE
      type within types.py, or the UPPERCASE type within
      the dialect itself if the type is not a standard SQL
      type.  This means reflection now returns more accurate
      information about reflected types.

    - Added a new Enum generic type. Enum is a schema-aware object
      to support databases which require specific DDL in order to
      use enum or equivalent; in the case of PG it handles the
      details of `CREATE TYPE`, and on other databases without
      native enum support will by generate VARCHAR + an inline CHECK
      constraint to enforce the enum.
      [ticket:1109] [ticket:1511]

    - The Interval type includes a "native" flag which controls
      if native INTERVAL types (postgresql + oracle) are selected
      if available, or not.  "day_precision" and "second_precision"
      arguments are also added which propagate as appropriately
      to these native types. Related to [ticket:1467].

    - The Boolean type, when used on a backend that doesn't
      have native boolean support, will generate a CHECK
      constraint "col IN (0, 1)" along with the int/smallint-
      based column type.  This can be switched off if
      desired with create_constraint=False.
      Note that MySQL has no native boolean *or* CHECK constraint
      support so this feature isn't available on that platform.
      [ticket:1589]

    - PickleType now uses == for comparison of values when
      mutable=True, unless the "comparator" argument with a
      comparsion function is specified to the type. Objects
      being pickled will be compared based on identity (which
      defeats the purpose of mutable=True) if __eq__() is not
      overridden or a comparison function is not provided.

    - The default "precision" and "scale" arguments of Numeric
      and Float have been removed and now default to None.
      NUMERIC and FLOAT will be rendered with no numeric
      arguments by default unless these values are provided.

    - AbstractType.get_search_list() is removed - the games
      that was used for are no longer necessary.

    - Added a generic BigInteger type, compiles to
      BIGINT or NUMBER(19). [ticket:1125]

-ext
    - sqlsoup has been overhauled to explicitly support an 0.5 style
      session, using autocommit=False, autoflush=True. Default
      behavior of SQLSoup now requires the usual usage of commit()
      and rollback(), which have been added to its interface. An
      explcit Session or scoped_session can be passed to the
      constructor, allowing these arguments to be overridden.

    - sqlsoup db.<sometable>.update() and delete() now call
      query(cls).update() and delete(), respectively.

    - sqlsoup now has execute() and connection(), which call upon
      the Session methods of those names, ensuring that the bind is
      in terms of the SqlSoup object's bind.

    - sqlsoup objects no longer have the 'query' attribute - it's
      not needed for sqlsoup's usage paradigm and it gets in the
      way of a column that is actually named 'query'.

    - The signature of the proxy_factory callable passed to
      association_proxy is now (lazy_collection, creator,
      value_attr, association_proxy), adding a fourth argument
      that is the parent AssociationProxy argument.  Allows
      serializability and subclassing of the built in collections.
      [ticket:1259]

    - association_proxy now has basic comparator methods .any(),
      .has(), .contains(), ==, !=, thanks to Scott Torborg.
      [ticket:1372]

- examples
    - The "query_cache" examples have been removed, and are replaced
      with a fully comprehensive approach that combines the usage of
      Beaker with SQLAlchemy.  New query options are used to indicate
      the caching characteristics of a particular Query, which
      can also be invoked deep within an object graph when lazily
      loading related objects.  See /examples/beaker_caching/README.

For changes prior to 0.6, see CHANGES_PRE_06